rename asyncio/ directory to trollius/

24 files changed, 11124 insertions, 0 deletions

diff --git a/trollius/__init__.py b/trollius/__init__.py
new file mode 100644
index 0000000..011466b
--- /dev/null
+++ b/trollius/__init__.py
@@ -0,0 +1,50 @@
+"""The asyncio package, tracking PEP 3156."""
+
+import sys
+
+# The selectors module is in the stdlib in Python 3.4 but not in 3.3.
+# Do this first, so the other submodules can use "from . import selectors".
+# Prefer asyncio/selectors.py over the stdlib one, as ours may be newer.
+try:
+    from . import selectors
+except ImportError:
+    import selectors  # Will also be exported.
+
+if sys.platform == 'win32':
+    # Similar thing for _overlapped.
+    try:
+        from . import _overlapped
+    except ImportError:
+        import _overlapped  # Will also be exported.
+
+# This relies on each of the submodules having an __all__ variable.
+from .base_events import *
+from .coroutines import *
+from .events import *
+from .futures import *
+from .locks import *
+from .protocols import *
+from .queues import *
+from .streams import *
+from .subprocess import *
+from .tasks import *
+from .transports import *
+
+__all__ = (base_events.__all__ +
+           coroutines.__all__ +
+           events.__all__ +
+           futures.__all__ +
+           locks.__all__ +
+           protocols.__all__ +
+           queues.__all__ +
+           streams.__all__ +
+           subprocess.__all__ +
+           tasks.__all__ +
+           transports.__all__)
+
+if sys.platform == 'win32':  # pragma: no cover
+    from .windows_events import *
+    __all__ += windows_events.__all__
+else:
+    from .unix_events import *  # pragma: no cover
+    __all__ += unix_events.__all__
diff --git a/trollius/base_events.py b/trollius/base_events.py
new file mode 100644
index 0000000..5a536a2
--- /dev/null
+++ b/trollius/base_events.py
@@ -0,0 +1,1240 @@
+"""Base implementation of event loop.
+
+The event loop can be broken up into a multiplexer (the part
+responsible for notifying us of I/O events) and the event loop proper,
+which wraps a multiplexer with functionality for scheduling callbacks,
+immediately or at a given time in the future.
+
+Whenever a public API takes a callback, subsequent positional
+arguments will be passed to the callback if/when it is called.  This
+avoids the proliferation of trivial lambdas implementing closures.
+Keyword arguments for the callback are not supported; this is a
+conscious design decision, leaving the door open for keyword arguments
+to modify the meaning of the API call itself.
+"""
+
+
+import collections
+import concurrent.futures
+import heapq
+import inspect
+import logging
+import os
+import socket
+import subprocess
+import threading
+import time
+import traceback
+import sys
+import warnings
+
+from . import coroutines
+from . import events
+from . import futures
+from . import tasks
+from .coroutines import coroutine
+from .log import logger
+
+
+__all__ = ['BaseEventLoop']
+
+
+# Argument for default thread pool executor creation.
+_MAX_WORKERS = 5
+
+# Minimum number of _scheduled timer handles before cleanup of
+# cancelled handles is performed.
+_MIN_SCHEDULED_TIMER_HANDLES = 100
+
+# Minimum fraction of _scheduled timer handles that are cancelled
+# before cleanup of cancelled handles is performed.
+_MIN_CANCELLED_TIMER_HANDLES_FRACTION = 0.5
+
+def _format_handle(handle):
+    cb = handle._callback
+    if inspect.ismethod(cb) and isinstance(cb.__self__, tasks.Task):
+        # format the task
+        return repr(cb.__self__)
+    else:
+        return str(handle)
+
+
+def _format_pipe(fd):
+    if fd == subprocess.PIPE:
+        return '<pipe>'
+    elif fd == subprocess.STDOUT:
+        return '<stdout>'
+    else:
+        return repr(fd)
+
+
+class _StopError(BaseException):
+    """Raised to stop the event loop."""
+
+
+def _check_resolved_address(sock, address):
+    # Ensure that the address is already resolved to avoid the trap of hanging
+    # the entire event loop when the address requires doing a DNS lookup.
+    #
+    # getaddrinfo() is slow (around 10 us per call): this function should only
+    # be called in debug mode
+    family = sock.family
+
+    if family == socket.AF_INET:
+        host, port = address
+    elif family == socket.AF_INET6:
+        host, port = address[:2]
+    else:
+        return
+
+    # On Windows, socket.inet_pton() is only available since Python 3.4
+    if hasattr(socket, 'inet_pton'):
+        # getaddrinfo() is slow and has known issue: prefer inet_pton()
+        # if available
+        try:
+            socket.inet_pton(family, host)
+        except OSError as exc:
+            raise ValueError("address must be resolved (IP address), "
+                             "got host %r: %s"
+                             % (host, exc))
+    else:
+        # Use getaddrinfo(flags=AI_NUMERICHOST) to ensure that the address is
+        # already resolved.
+        type_mask = 0
+        if hasattr(socket, 'SOCK_NONBLOCK'):
+            type_mask |= socket.SOCK_NONBLOCK
+        if hasattr(socket, 'SOCK_CLOEXEC'):
+            type_mask |= socket.SOCK_CLOEXEC
+        try:
+            socket.getaddrinfo(host, port,
+                               family=family,
+                               type=(sock.type & ~type_mask),
+                               proto=sock.proto,
+                               flags=socket.AI_NUMERICHOST)
+        except socket.gaierror as err:
+            raise ValueError("address must be resolved (IP address), "
+                             "got host %r: %s"
+                             % (host, err))
+
+def _raise_stop_error(*args):
+    raise _StopError
+
+
+def _run_until_complete_cb(fut):
+    exc = fut._exception
+    if (isinstance(exc, BaseException)
+    and not isinstance(exc, Exception)):
+        # Issue #22429: run_forever() already finished, no need to
+        # stop it.
+        return
+    _raise_stop_error()
+
+
+class Server(events.AbstractServer):
+
+    def __init__(self, loop, sockets):
+        self._loop = loop
+        self.sockets = sockets
+        self._active_count = 0
+        self._waiters = []
+
+    def __repr__(self):
+        return '<%s sockets=%r>' % (self.__class__.__name__, self.sockets)
+
+    def _attach(self):
+        assert self.sockets is not None
+        self._active_count += 1
+
+    def _detach(self):
+        assert self._active_count > 0
+        self._active_count -= 1
+        if self._active_count == 0 and self.sockets is None:
+            self._wakeup()
+
+    def close(self):
+        sockets = self.sockets
+        if sockets is None:
+            return
+        self.sockets = None
+        for sock in sockets:
+            self._loop._stop_serving(sock)
+        if self._active_count == 0:
+            self._wakeup()
+
+    def _wakeup(self):
+        waiters = self._waiters
+        self._waiters = None
+        for waiter in waiters:
+            if not waiter.done():
+                waiter.set_result(waiter)
+
+    @coroutine
+    def wait_closed(self):
+        if self.sockets is None or self._waiters is None:
+            return
+        waiter = futures.Future(loop=self._loop)
+        self._waiters.append(waiter)
+        yield from waiter
+
+
+class BaseEventLoop(events.AbstractEventLoop):
+
+    def __init__(self):
+        self._timer_cancelled_count = 0
+        self._closed = False
+        self._ready = collections.deque()
+        self._scheduled = []
+        self._default_executor = None
+        self._internal_fds = 0
+        # Identifier of the thread running the event loop, or None if the
+        # event loop is not running
+        self._thread_id = None
+        self._clock_resolution = time.get_clock_info('monotonic').resolution
+        self._exception_handler = None
+        self.set_debug((not sys.flags.ignore_environment
+                        and bool(os.environ.get('PYTHONASYNCIODEBUG'))))
+        # In debug mode, if the execution of a callback or a step of a task
+        # exceed this duration in seconds, the slow callback/task is logged.
+        self.slow_callback_duration = 0.1
+        self._current_handle = None
+        self._task_factory = None
+        self._coroutine_wrapper_set = False
+
+    def __repr__(self):
+        return ('<%s running=%s closed=%s debug=%s>'
+                % (self.__class__.__name__, self.is_running(),
+                   self.is_closed(), self.get_debug()))
+
+    def create_task(self, coro):
+        """Schedule a coroutine object.
+
+        Return a task object.
+        """
+        self._check_closed()
+        if self._task_factory is None:
+            task = tasks.Task(coro, loop=self)
+            if task._source_traceback:
+                del task._source_traceback[-1]
+        else:
+            task = self._task_factory(self, coro)
+        return task
+
+    def set_task_factory(self, factory):
+        """Set a task factory that will be used by loop.create_task().
+
+        If factory is None the default task factory will be set.
+
+        If factory is a callable, it should have a signature matching
+        '(loop, coro)', where 'loop' will be a reference to the active
+        event loop, 'coro' will be a coroutine object.  The callable
+        must return a Future.
+        """
+        if factory is not None and not callable(factory):
+            raise TypeError('task factory must be a callable or None')
+        self._task_factory = factory
+
+    def get_task_factory(self):
+        """Return a task factory, or None if the default one is in use."""
+        return self._task_factory
+
+    def _make_socket_transport(self, sock, protocol, waiter=None, *,
+                               extra=None, server=None):
+        """Create socket transport."""
+        raise NotImplementedError
+
+    def _make_ssl_transport(self, rawsock, protocol, sslcontext, waiter=None,
+                            *, server_side=False, server_hostname=None,
+                            extra=None, server=None):
+        """Create SSL transport."""
+        raise NotImplementedError
+
+    def _make_datagram_transport(self, sock, protocol,
+                                 address=None, waiter=None, extra=None):
+        """Create datagram transport."""
+        raise NotImplementedError
+
+    def _make_read_pipe_transport(self, pipe, protocol, waiter=None,
+                                  extra=None):
+        """Create read pipe transport."""
+        raise NotImplementedError
+
+    def _make_write_pipe_transport(self, pipe, protocol, waiter=None,
+                                   extra=None):
+        """Create write pipe transport."""
+        raise NotImplementedError
+
+    @coroutine
+    def _make_subprocess_transport(self, protocol, args, shell,
+                                   stdin, stdout, stderr, bufsize,
+                                   extra=None, **kwargs):
+        """Create subprocess transport."""
+        raise NotImplementedError
+
+    def _write_to_self(self):
+        """Write a byte to self-pipe, to wake up the event loop.
+
+        This may be called from a different thread.
+
+        The subclass is responsible for implementing the self-pipe.
+        """
+        raise NotImplementedError
+
+    def _process_events(self, event_list):
+        """Process selector events."""
+        raise NotImplementedError
+
+    def _check_closed(self):
+        if self._closed:
+            raise RuntimeError('Event loop is closed')
+
+    def run_forever(self):
+        """Run until stop() is called."""
+        self._check_closed()
+        if self.is_running():
+            raise RuntimeError('Event loop is running.')
+        self._set_coroutine_wrapper(self._debug)
+        self._thread_id = threading.get_ident()
+        try:
+            while True:
+                try:
+                    self._run_once()
+                except _StopError:
+                    break
+        finally:
+            self._thread_id = None
+            self._set_coroutine_wrapper(False)
+
+    def run_until_complete(self, future):
+        """Run until the Future is done.
+
+        If the argument is a coroutine, it is wrapped in a Task.
+
+        WARNING: It would be disastrous to call run_until_complete()
+        with the same coroutine twice -- it would wrap it in two
+        different Tasks and that can't be good.
+
+        Return the Future's result, or raise its exception.
+        """
+        self._check_closed()
+
+        new_task = not isinstance(future, futures.Future)
+        future = tasks.ensure_future(future, loop=self)
+        if new_task:
+            # An exception is raised if the future didn't complete, so there
+            # is no need to log the "destroy pending task" message
+            future._log_destroy_pending = False
+
+        future.add_done_callback(_run_until_complete_cb)
+        try:
+            self.run_forever()
+        except:
+            if new_task and future.done() and not future.cancelled():
+                # The coroutine raised a BaseException. Consume the exception
+                # to not log a warning, the caller doesn't have access to the
+                # local task.
+                future.exception()
+            raise
+        future.remove_done_callback(_run_until_complete_cb)
+        if not future.done():
+            raise RuntimeError('Event loop stopped before Future completed.')
+
+        return future.result()
+
+    def stop(self):
+        """Stop running the event loop.
+
+        Every callback scheduled before stop() is called will run. Callbacks
+        scheduled after stop() is called will not run. However, those callbacks
+        will run if run_forever is called again later.
+        """
+        self.call_soon(_raise_stop_error)
+
+    def close(self):
+        """Close the event loop.
+
+        This clears the queues and shuts down the executor,
+        but does not wait for the executor to finish.
+
+        The event loop must not be running.
+        """
+        if self.is_running():
+            raise RuntimeError("Cannot close a running event loop")
+        if self._closed:
+            return
+        if self._debug:
+            logger.debug("Close %r", self)
+        self._closed = True
+        self._ready.clear()
+        self._scheduled.clear()
+        executor = self._default_executor
+        if executor is not None:
+            self._default_executor = None
+            executor.shutdown(wait=False)
+
+    def is_closed(self):
+        """Returns True if the event loop was closed."""
+        return self._closed
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if not self.is_closed():
+                warnings.warn("unclosed event loop %r" % self, ResourceWarning)
+                if not self.is_running():
+                    self.close()
+
+    def is_running(self):
+        """Returns True if the event loop is running."""
+        return (self._thread_id is not None)
+
+    def time(self):
+        """Return the time according to the event loop's clock.
+
+        This is a float expressed in seconds since an epoch, but the
+        epoch, precision, accuracy and drift are unspecified and may
+        differ per event loop.
+        """
+        return time.monotonic()
+
+    def call_later(self, delay, callback, *args):
+        """Arrange for a callback to be called at a given time.
+
+        Return a Handle: an opaque object with a cancel() method that
+        can be used to cancel the call.
+
+        The delay can be an int or float, expressed in seconds.  It is
+        always relative to the current time.
+
+        Each callback will be called exactly once.  If two callbacks
+        are scheduled for exactly the same time, it undefined which
+        will be called first.
+
+        Any positional arguments after the callback will be passed to
+        the callback when it is called.
+        """
+        timer = self.call_at(self.time() + delay, callback, *args)
+        if timer._source_traceback:
+            del timer._source_traceback[-1]
+        return timer
+
+    def call_at(self, when, callback, *args):
+        """Like call_later(), but uses an absolute time.
+
+        Absolute time corresponds to the event loop's time() method.
+        """
+        if (coroutines.iscoroutine(callback)
+        or coroutines.iscoroutinefunction(callback)):
+            raise TypeError("coroutines cannot be used with call_at()")
+        self._check_closed()
+        if self._debug:
+            self._check_thread()
+        timer = events.TimerHandle(when, callback, args, self)
+        if timer._source_traceback:
+            del timer._source_traceback[-1]
+        heapq.heappush(self._scheduled, timer)
+        timer._scheduled = True
+        return timer
+
+    def call_soon(self, callback, *args):
+        """Arrange for a callback to be called as soon as possible.
+
+        This operates as a FIFO queue: callbacks are called in the
+        order in which they are registered.  Each callback will be
+        called exactly once.
+
+        Any positional arguments after the callback will be passed to
+        the callback when it is called.
+        """
+        if self._debug:
+            self._check_thread()
+        handle = self._call_soon(callback, args)
+        if handle._source_traceback:
+            del handle._source_traceback[-1]
+        return handle
+
+    def _call_soon(self, callback, args):
+        if (coroutines.iscoroutine(callback)
+        or coroutines.iscoroutinefunction(callback)):
+            raise TypeError("coroutines cannot be used with call_soon()")
+        self._check_closed()
+        handle = events.Handle(callback, args, self)
+        if handle._source_traceback:
+            del handle._source_traceback[-1]
+        self._ready.append(handle)
+        return handle
+
+    def _check_thread(self):
+        """Check that the current thread is the thread running the event loop.
+
+        Non-thread-safe methods of this class make this assumption and will
+        likely behave incorrectly when the assumption is violated.
+
+        Should only be called when (self._debug == True).  The caller is
+        responsible for checking this condition for performance reasons.
+        """
+        if self._thread_id is None:
+            return
+        thread_id = threading.get_ident()
+        if thread_id != self._thread_id:
+            raise RuntimeError(
+                "Non-thread-safe operation invoked on an event loop other "
+                "than the current one")
+
+    def call_soon_threadsafe(self, callback, *args):
+        """Like call_soon(), but thread-safe."""
+        handle = self._call_soon(callback, args)
+        if handle._source_traceback:
+            del handle._source_traceback[-1]
+        self._write_to_self()
+        return handle
+
+    def run_in_executor(self, executor, func, *args):
+        if (coroutines.iscoroutine(func)
+        or coroutines.iscoroutinefunction(func)):
+            raise TypeError("coroutines cannot be used with run_in_executor()")
+        self._check_closed()
+        if isinstance(func, events.Handle):
+            assert not args
+            assert not isinstance(func, events.TimerHandle)
+            if func._cancelled:
+                f = futures.Future(loop=self)
+                f.set_result(None)
+                return f
+            func, args = func._callback, func._args
+        if executor is None:
+            executor = self._default_executor
+            if executor is None:
+                executor = concurrent.futures.ThreadPoolExecutor(_MAX_WORKERS)
+                self._default_executor = executor
+        return futures.wrap_future(executor.submit(func, *args), loop=self)
+
+    def set_default_executor(self, executor):
+        self._default_executor = executor
+
+    def _getaddrinfo_debug(self, host, port, family, type, proto, flags):
+        msg = ["%s:%r" % (host, port)]
+        if family:
+            msg.append('family=%r' % family)
+        if type:
+            msg.append('type=%r' % type)
+        if proto:
+            msg.append('proto=%r' % proto)
+        if flags:
+            msg.append('flags=%r' % flags)
+        msg = ', '.join(msg)
+        logger.debug('Get address info %s', msg)
+
+        t0 = self.time()
+        addrinfo = socket.getaddrinfo(host, port, family, type, proto, flags)
+        dt = self.time() - t0
+
+        msg = ('Getting address info %s took %.3f ms: %r'
+               % (msg, dt * 1e3, addrinfo))
+        if dt >= self.slow_callback_duration:
+            logger.info(msg)
+        else:
+            logger.debug(msg)
+        return addrinfo
+
+    def getaddrinfo(self, host, port, *,
+                    family=0, type=0, proto=0, flags=0):
+        if self._debug:
+            return self.run_in_executor(None, self._getaddrinfo_debug,
+                                        host, port, family, type, proto, flags)
+        else:
+            return self.run_in_executor(None, socket.getaddrinfo,
+                                        host, port, family, type, proto, flags)
+
+    def getnameinfo(self, sockaddr, flags=0):
+        return self.run_in_executor(None, socket.getnameinfo, sockaddr, flags)
+
+    @coroutine
+    def create_connection(self, protocol_factory, host=None, port=None, *,
+                          ssl=None, family=0, proto=0, flags=0, sock=None,
+                          local_addr=None, server_hostname=None):
+        """Connect to a TCP server.
+
+        Create a streaming transport connection to a given Internet host and
+        port: socket family AF_INET or socket.AF_INET6 depending on host (or
+        family if specified), socket type SOCK_STREAM. protocol_factory must be
+        a callable returning a protocol instance.
+
+        This method is a coroutine which will try to establish the connection
+        in the background.  When successful, the coroutine returns a
+        (transport, protocol) pair.
+        """
+        if server_hostname is not None and not ssl:
+            raise ValueError('server_hostname is only meaningful with ssl')
+
+        if server_hostname is None and ssl:
+            # Use host as default for server_hostname.  It is an error
+            # if host is empty or not set, e.g. when an
+            # already-connected socket was passed or when only a port
+            # is given.  To avoid this error, you can pass
+            # server_hostname='' -- this will bypass the hostname
+            # check.  (This also means that if host is a numeric
+            # IP/IPv6 address, we will attempt to verify that exact
+            # address; this will probably fail, but it is possible to
+            # create a certificate for a specific IP address, so we
+            # don't judge it here.)
+            if not host:
+                raise ValueError('You must set server_hostname '
+                                 'when using ssl without a host')
+            server_hostname = host
+
+        if host is not None or port is not None:
+            if sock is not None:
+                raise ValueError(
+                    'host/port and sock can not be specified at the same time')
+
+            f1 = self.getaddrinfo(
+                host, port, family=family,
+                type=socket.SOCK_STREAM, proto=proto, flags=flags)
+            fs = [f1]
+            if local_addr is not None:
+                f2 = self.getaddrinfo(
+                    *local_addr, family=family,
+                    type=socket.SOCK_STREAM, proto=proto, flags=flags)
+                fs.append(f2)
+            else:
+                f2 = None
+
+            yield from tasks.wait(fs, loop=self)
+
+            infos = f1.result()
+            if not infos:
+                raise OSError('getaddrinfo() returned empty list')
+            if f2 is not None:
+                laddr_infos = f2.result()
+                if not laddr_infos:
+                    raise OSError('getaddrinfo() returned empty list')
+
+            exceptions = []
+            for family, type, proto, cname, address in infos:
+                try:
+                    sock = socket.socket(family=family, type=type, proto=proto)
+                    sock.setblocking(False)
+                    if f2 is not None:
+                        for _, _, _, _, laddr in laddr_infos:
+                            try:
+                                sock.bind(laddr)
+                                break
+                            except OSError as exc:
+                                exc = OSError(
+                                    exc.errno, 'error while '
+                                    'attempting to bind on address '
+                                    '{!r}: {}'.format(
+                                        laddr, exc.strerror.lower()))
+                                exceptions.append(exc)
+                        else:
+                            sock.close()
+                            sock = None
+                            continue
+                    if self._debug:
+                        logger.debug("connect %r to %r", sock, address)
+                    yield from self.sock_connect(sock, address)
+                except OSError as exc:
+                    if sock is not None:
+                        sock.close()
+                    exceptions.append(exc)
+                except:
+                    if sock is not None:
+                        sock.close()
+                    raise
+                else:
+                    break
+            else:
+                if len(exceptions) == 1:
+                    raise exceptions[0]
+                else:
+                    # If they all have the same str(), raise one.
+                    model = str(exceptions[0])
+                    if all(str(exc) == model for exc in exceptions):
+                        raise exceptions[0]
+                    # Raise a combined exception so the user can see all
+                    # the various error messages.
+                    raise OSError('Multiple exceptions: {}'.format(
+                        ', '.join(str(exc) for exc in exceptions)))
+
+        elif sock is None:
+            raise ValueError(
+                'host and port was not specified and no sock specified')
+
+        sock.setblocking(False)
+
+        transport, protocol = yield from self._create_connection_transport(
+            sock, protocol_factory, ssl, server_hostname)
+        if self._debug:
+            # Get the socket from the transport because SSL transport closes
+            # the old socket and creates a new SSL socket
+            sock = transport.get_extra_info('socket')
+            logger.debug("%r connected to %s:%r: (%r, %r)",
+                         sock, host, port, transport, protocol)
+        return transport, protocol
+
+    @coroutine
+    def _create_connection_transport(self, sock, protocol_factory, ssl,
+                                     server_hostname):
+        protocol = protocol_factory()
+        waiter = futures.Future(loop=self)
+        if ssl:
+            sslcontext = None if isinstance(ssl, bool) else ssl
+            transport = self._make_ssl_transport(
+                sock, protocol, sslcontext, waiter,
+                server_side=False, server_hostname=server_hostname)
+        else:
+            transport = self._make_socket_transport(sock, protocol, waiter)
+
+        try:
+            yield from waiter
+        except:
+            transport.close()
+            raise
+
+        return transport, protocol
+
+    @coroutine
+    def create_datagram_endpoint(self, protocol_factory,
+                                 local_addr=None, remote_addr=None, *,
+                                 family=0, proto=0, flags=0):
+        """Create datagram connection."""
+        if not (local_addr or remote_addr):
+            if family == 0:
+                raise ValueError('unexpected address family')
+            addr_pairs_info = (((family, proto), (None, None)),)
+        else:
+            # join address by (family, protocol)
+            addr_infos = collections.OrderedDict()
+            for idx, addr in ((0, local_addr), (1, remote_addr)):
+                if addr is not None:
+                    assert isinstance(addr, tuple) and len(addr) == 2, (
+                        '2-tuple is expected')
+
+                    infos = yield from self.getaddrinfo(
+                        *addr, family=family, type=socket.SOCK_DGRAM,
+                        proto=proto, flags=flags)
+                    if not infos:
+                        raise OSError('getaddrinfo() returned empty list')
+
+                    for fam, _, pro, _, address in infos:
+                        key = (fam, pro)
+                        if key not in addr_infos:
+                            addr_infos[key] = [None, None]
+                        addr_infos[key][idx] = address
+
+            # each addr has to have info for each (family, proto) pair
+            addr_pairs_info = [
+                (key, addr_pair) for key, addr_pair in addr_infos.items()
+                if not ((local_addr and addr_pair[0] is None) or
+                        (remote_addr and addr_pair[1] is None))]
+
+            if not addr_pairs_info:
+                raise ValueError('can not get address information')
+
+        exceptions = []
+
+        for ((family, proto),
+             (local_address, remote_address)) in addr_pairs_info:
+            sock = None
+            r_addr = None
+            try:
+                sock = socket.socket(
+                    family=family, type=socket.SOCK_DGRAM, proto=proto)
+                sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+                sock.setblocking(False)
+
+                if local_addr:
+                    sock.bind(local_address)
+                if remote_addr:
+                    yield from self.sock_connect(sock, remote_address)
+                    r_addr = remote_address
+            except OSError as exc:
+                if sock is not None:
+                    sock.close()
+                exceptions.append(exc)
+            except:
+                if sock is not None:
+                    sock.close()
+                raise
+            else:
+                break
+        else:
+            raise exceptions[0]
+
+        protocol = protocol_factory()
+        waiter = futures.Future(loop=self)
+        transport = self._make_datagram_transport(sock, protocol, r_addr,
+                                                  waiter)
+        if self._debug:
+            if local_addr:
+                logger.info("Datagram endpoint local_addr=%r remote_addr=%r "
+                            "created: (%r, %r)",
+                            local_addr, remote_addr, transport, protocol)
+            else:
+                logger.debug("Datagram endpoint remote_addr=%r created: "
+                             "(%r, %r)",
+                             remote_addr, transport, protocol)
+
+        try:
+            yield from waiter
+        except:
+            transport.close()
+            raise
+
+        return transport, protocol
+
+    @coroutine
+    def create_server(self, protocol_factory, host=None, port=None,
+                      *,
+                      family=socket.AF_UNSPEC,
+                      flags=socket.AI_PASSIVE,
+                      sock=None,
+                      backlog=100,
+                      ssl=None,
+                      reuse_address=None):
+        """Create a TCP server bound to host and port.
+
+        Return a Server object which can be used to stop the service.
+
+        This method is a coroutine.
+        """
+        if isinstance(ssl, bool):
+            raise TypeError('ssl argument must be an SSLContext or None')
+        if host is not None or port is not None:
+            if sock is not None:
+                raise ValueError(
+                    'host/port and sock can not be specified at the same time')
+
+            AF_INET6 = getattr(socket, 'AF_INET6', 0)
+            if reuse_address is None:
+                reuse_address = os.name == 'posix' and sys.platform != 'cygwin'
+            sockets = []
+            if host == '':
+                host = None
+
+            infos = yield from self.getaddrinfo(
+                host, port, family=family,
+                type=socket.SOCK_STREAM, proto=0, flags=flags)
+            if not infos:
+                raise OSError('getaddrinfo() returned empty list')
+
+            completed = False
+            try:
+                for res in infos:
+                    af, socktype, proto, canonname, sa = res
+                    try:
+                        sock = socket.socket(af, socktype, proto)
+                    except socket.error:
+                        # Assume it's a bad family/type/protocol combination.
+                        if self._debug:
+                            logger.warning('create_server() failed to create '
+                                           'socket.socket(%r, %r, %r)',
+                                           af, socktype, proto, exc_info=True)
+                        continue
+                    sockets.append(sock)
+                    if reuse_address:
+                        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR,
+                                        True)
+                    # Disable IPv4/IPv6 dual stack support (enabled by
+                    # default on Linux) which makes a single socket
+                    # listen on both address families.
+                    if af == AF_INET6 and hasattr(socket, 'IPPROTO_IPV6'):
+                        sock.setsockopt(socket.IPPROTO_IPV6,
+                                        socket.IPV6_V6ONLY,
+                                        True)
+                    try:
+                        sock.bind(sa)
+                    except OSError as err:
+                        raise OSError(err.errno, 'error while attempting '
+                                      'to bind on address %r: %s'
+                                      % (sa, err.strerror.lower()))
+                completed = True
+            finally:
+                if not completed:
+                    for sock in sockets:
+                        sock.close()
+        else:
+            if sock is None:
+                raise ValueError('Neither host/port nor sock were specified')
+            sockets = [sock]
+
+        server = Server(self, sockets)
+        for sock in sockets:
+            sock.listen(backlog)
+            sock.setblocking(False)
+            self._start_serving(protocol_factory, sock, ssl, server)
+        if self._debug:
+            logger.info("%r is serving", server)
+        return server
+
+    @coroutine
+    def connect_read_pipe(self, protocol_factory, pipe):
+        protocol = protocol_factory()
+        waiter = futures.Future(loop=self)
+        transport = self._make_read_pipe_transport(pipe, protocol, waiter)
+
+        try:
+            yield from waiter
+        except:
+            transport.close()
+            raise
+
+        if self._debug:
+            logger.debug('Read pipe %r connected: (%r, %r)',
+                         pipe.fileno(), transport, protocol)
+        return transport, protocol
+
+    @coroutine
+    def connect_write_pipe(self, protocol_factory, pipe):
+        protocol = protocol_factory()
+        waiter = futures.Future(loop=self)
+        transport = self._make_write_pipe_transport(pipe, protocol, waiter)
+
+        try:
+            yield from waiter
+        except:
+            transport.close()
+            raise
+
+        if self._debug:
+            logger.debug('Write pipe %r connected: (%r, %r)',
+                         pipe.fileno(), transport, protocol)
+        return transport, protocol
+
+    def _log_subprocess(self, msg, stdin, stdout, stderr):
+        info = [msg]
+        if stdin is not None:
+            info.append('stdin=%s' % _format_pipe(stdin))
+        if stdout is not None and stderr == subprocess.STDOUT:
+            info.append('stdout=stderr=%s' % _format_pipe(stdout))
+        else:
+            if stdout is not None:
+                info.append('stdout=%s' % _format_pipe(stdout))
+            if stderr is not None:
+                info.append('stderr=%s' % _format_pipe(stderr))
+        logger.debug(' '.join(info))
+
+    @coroutine
+    def subprocess_shell(self, protocol_factory, cmd, *, stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                         universal_newlines=False, shell=True, bufsize=0,
+                         **kwargs):
+        if not isinstance(cmd, (bytes, str)):
+            raise ValueError("cmd must be a string")
+        if universal_newlines:
+            raise ValueError("universal_newlines must be False")
+        if not shell:
+            raise ValueError("shell must be True")
+        if bufsize != 0:
+            raise ValueError("bufsize must be 0")
+        protocol = protocol_factory()
+        if self._debug:
+            # don't log parameters: they may contain sensitive information
+            # (password) and may be too long
+            debug_log = 'run shell command %r' % cmd
+            self._log_subprocess(debug_log, stdin, stdout, stderr)
+        transport = yield from self._make_subprocess_transport(
+            protocol, cmd, True, stdin, stdout, stderr, bufsize, **kwargs)
+        if self._debug:
+            logger.info('%s: %r' % (debug_log, transport))
+        return transport, protocol
+
+    @coroutine
+    def subprocess_exec(self, protocol_factory, program, *args,
+                        stdin=subprocess.PIPE, stdout=subprocess.PIPE,
+                        stderr=subprocess.PIPE, universal_newlines=False,
+                        shell=False, bufsize=0, **kwargs):
+        if universal_newlines:
+            raise ValueError("universal_newlines must be False")
+        if shell:
+            raise ValueError("shell must be False")
+        if bufsize != 0:
+            raise ValueError("bufsize must be 0")
+        popen_args = (program,) + args
+        for arg in popen_args:
+            if not isinstance(arg, (str, bytes)):
+                raise TypeError("program arguments must be "
+                                "a bytes or text string, not %s"
+                                % type(arg).__name__)
+        protocol = protocol_factory()
+        if self._debug:
+            # don't log parameters: they may contain sensitive information
+            # (password) and may be too long
+            debug_log = 'execute program %r' % program
+            self._log_subprocess(debug_log, stdin, stdout, stderr)
+        transport = yield from self._make_subprocess_transport(
+            protocol, popen_args, False, stdin, stdout, stderr,
+            bufsize, **kwargs)
+        if self._debug:
+            logger.info('%s: %r' % (debug_log, transport))
+        return transport, protocol
+
+    def set_exception_handler(self, handler):
+        """Set handler as the new event loop exception handler.
+
+        If handler is None, the default exception handler will
+        be set.
+
+        If handler is a callable object, it should have a
+        signature matching '(loop, context)', where 'loop'
+        will be a reference to the active event loop, 'context'
+        will be a dict object (see `call_exception_handler()`
+        documentation for details about context).
+        """
+        if handler is not None and not callable(handler):
+            raise TypeError('A callable object or None is expected, '
+                            'got {!r}'.format(handler))
+        self._exception_handler = handler
+
+    def default_exception_handler(self, context):
+        """Default exception handler.
+
+        This is called when an exception occurs and no exception
+        handler is set, and can be called by a custom exception
+        handler that wants to defer to the default behavior.
+
+        The context parameter has the same meaning as in
+        `call_exception_handler()`.
+        """
+        message = context.get('message')
+        if not message:
+            message = 'Unhandled exception in event loop'
+
+        exception = context.get('exception')
+        if exception is not None:
+            exc_info = (type(exception), exception, exception.__traceback__)
+        else:
+            exc_info = False
+
+        if ('source_traceback' not in context
+        and self._current_handle is not None
+        and self._current_handle._source_traceback):
+            context['handle_traceback'] = self._current_handle._source_traceback
+
+        log_lines = [message]
+        for key in sorted(context):
+            if key in {'message', 'exception'}:
+                continue
+            value = context[key]
+            if key == 'source_traceback':
+                tb = ''.join(traceback.format_list(value))
+                value = 'Object created at (most recent call last):\n'
+                value += tb.rstrip()
+            elif key == 'handle_traceback':
+                tb = ''.join(traceback.format_list(value))
+                value = 'Handle created at (most recent call last):\n'
+                value += tb.rstrip()
+            else:
+                value = repr(value)
+            log_lines.append('{}: {}'.format(key, value))
+
+        logger.error('\n'.join(log_lines), exc_info=exc_info)
+
+    def call_exception_handler(self, context):
+        """Call the current event loop's exception handler.
+
+        The context argument is a dict containing the following keys:
+
+        - 'message': Error message;
+        - 'exception' (optional): Exception object;
+        - 'future' (optional): Future instance;
+        - 'handle' (optional): Handle instance;
+        - 'protocol' (optional): Protocol instance;
+        - 'transport' (optional): Transport instance;
+        - 'socket' (optional): Socket instance.
+
+        New keys maybe introduced in the future.
+
+        Note: do not overload this method in an event loop subclass.
+        For custom exception handling, use the
+        `set_exception_handler()` method.
+        """
+        if self._exception_handler is None:
+            try:
+                self.default_exception_handler(context)
+            except Exception:
+                # Second protection layer for unexpected errors
+                # in the default implementation, as well as for subclassed
+                # event loops with overloaded "default_exception_handler".
+                logger.error('Exception in default exception handler',
+                             exc_info=True)
+        else:
+            try:
+                self._exception_handler(self, context)
+            except Exception as exc:
+                # Exception in the user set custom exception handler.
+                try:
+                    # Let's try default handler.
+                    self.default_exception_handler({
+                        'message': 'Unhandled error in exception handler',
+                        'exception': exc,
+                        'context': context,
+                    })
+                except Exception:
+                    # Guard 'default_exception_handler' in case it is
+                    # overloaded.
+                    logger.error('Exception in default exception handler '
+                                 'while handling an unexpected error '
+                                 'in custom exception handler',
+                                 exc_info=True)
+
+    def _add_callback(self, handle):
+        """Add a Handle to _scheduled (TimerHandle) or _ready."""
+        assert isinstance(handle, events.Handle), 'A Handle is required here'
+        if handle._cancelled:
+            return
+        assert not isinstance(handle, events.TimerHandle)
+        self._ready.append(handle)
+
+    def _add_callback_signalsafe(self, handle):
+        """Like _add_callback() but called from a signal handler."""
+        self._add_callback(handle)
+        self._write_to_self()
+
+    def _timer_handle_cancelled(self, handle):
+        """Notification that a TimerHandle has been cancelled."""
+        if handle._scheduled:
+            self._timer_cancelled_count += 1
+
+    def _run_once(self):
+        """Run one full iteration of the event loop.
+
+        This calls all currently ready callbacks, polls for I/O,
+        schedules the resulting callbacks, and finally schedules
+        'call_later' callbacks.
+        """
+
+        sched_count = len(self._scheduled)
+        if (sched_count > _MIN_SCHEDULED_TIMER_HANDLES and
+            self._timer_cancelled_count / sched_count >
+                _MIN_CANCELLED_TIMER_HANDLES_FRACTION):
+            # Remove delayed calls that were cancelled if their number
+            # is too high
+            new_scheduled = []
+            for handle in self._scheduled:
+                if handle._cancelled:
+                    handle._scheduled = False
+                else:
+                    new_scheduled.append(handle)
+
+            heapq.heapify(new_scheduled)
+            self._scheduled = new_scheduled
+            self._timer_cancelled_count = 0
+        else:
+            # Remove delayed calls that were cancelled from head of queue.
+            while self._scheduled and self._scheduled[0]._cancelled:
+                self._timer_cancelled_count -= 1
+                handle = heapq.heappop(self._scheduled)
+                handle._scheduled = False
+
+        timeout = None
+        if self._ready:
+            timeout = 0
+        elif self._scheduled:
+            # Compute the desired timeout.
+            when = self._scheduled[0]._when
+            timeout = max(0, when - self.time())
+
+        if self._debug and timeout != 0:
+            t0 = self.time()
+            event_list = self._selector.select(timeout)
+            dt = self.time() - t0
+            if dt >= 1.0:
+                level = logging.INFO
+            else:
+                level = logging.DEBUG
+            nevent = len(event_list)
+            if timeout is None:
+                logger.log(level, 'poll took %.3f ms: %s events',
+                           dt * 1e3, nevent)
+            elif nevent:
+                logger.log(level,
+                           'poll %.3f ms took %.3f ms: %s events',
+                           timeout * 1e3, dt * 1e3, nevent)
+            elif dt >= 1.0:
+                logger.log(level,
+                           'poll %.3f ms took %.3f ms: timeout',
+                           timeout * 1e3, dt * 1e3)
+        else:
+            event_list = self._selector.select(timeout)
+        self._process_events(event_list)
+
+        # Handle 'later' callbacks that are ready.
+        end_time = self.time() + self._clock_resolution
+        while self._scheduled:
+            handle = self._scheduled[0]
+            if handle._when >= end_time:
+                break
+            handle = heapq.heappop(self._scheduled)
+            handle._scheduled = False
+            self._ready.append(handle)
+
+        # This is the only place where callbacks are actually *called*.
+        # All other places just add them to ready.
+        # Note: We run all currently scheduled callbacks, but not any
+        # callbacks scheduled by callbacks run this time around --
+        # they will be run the next time (after another I/O poll).
+        # Use an idiom that is thread-safe without using locks.
+        ntodo = len(self._ready)
+        for i in range(ntodo):
+            handle = self._ready.popleft()
+            if handle._cancelled:
+                continue
+            if self._debug:
+                try:
+                    self._current_handle = handle
+                    t0 = self.time()
+                    handle._run()
+                    dt = self.time() - t0
+                    if dt >= self.slow_callback_duration:
+                        logger.warning('Executing %s took %.3f seconds',
+                                       _format_handle(handle), dt)
+                finally:
+                    self._current_handle = None
+            else:
+                handle._run()
+        handle = None  # Needed to break cycles when an exception occurs.
+
+    def _set_coroutine_wrapper(self, enabled):
+        try:
+            set_wrapper = sys.set_coroutine_wrapper
+            get_wrapper = sys.get_coroutine_wrapper
+        except AttributeError:
+            return
+
+        enabled = bool(enabled)
+        if self._coroutine_wrapper_set is enabled:
+            return
+
+        wrapper = coroutines.debug_wrapper
+        current_wrapper = get_wrapper()
+
+        if enabled:
+            if current_wrapper not in (None, wrapper):
+                warnings.warn(
+                    "loop.set_debug(True): cannot set debug coroutine "
+                    "wrapper; another wrapper is already set %r" %
+                    current_wrapper, RuntimeWarning)
+            else:
+                set_wrapper(wrapper)
+                self._coroutine_wrapper_set = True
+        else:
+            if current_wrapper not in (None, wrapper):
+                warnings.warn(
+                    "loop.set_debug(False): cannot unset debug coroutine "
+                    "wrapper; another wrapper was set %r" %
+                    current_wrapper, RuntimeWarning)
+            else:
+                set_wrapper(None)
+                self._coroutine_wrapper_set = False
+
+    def get_debug(self):
+        return self._debug
+
+    def set_debug(self, enabled):
+        self._debug = enabled
+
+        if self.is_running():
+            self._set_coroutine_wrapper(enabled)
diff --git a/trollius/base_subprocess.py b/trollius/base_subprocess.py
new file mode 100644
index 0000000..c1477b8
--- /dev/null
+++ b/trollius/base_subprocess.py
@@ -0,0 +1,275 @@
+import collections
+import subprocess
+import sys
+import warnings
+
+from . import futures
+from . import protocols
+from . import transports
+from .coroutines import coroutine
+from .log import logger
+
+
+class BaseSubprocessTransport(transports.SubprocessTransport):
+
+    def __init__(self, loop, protocol, args, shell,
+                 stdin, stdout, stderr, bufsize,
+                 waiter=None, extra=None, **kwargs):
+        super().__init__(extra)
+        self._closed = False
+        self._protocol = protocol
+        self._loop = loop
+        self._proc = None
+        self._pid = None
+        self._returncode = None
+        self._exit_waiters = []
+        self._pending_calls = collections.deque()
+        self._pipes = {}
+        self._finished = False
+
+        if stdin == subprocess.PIPE:
+            self._pipes[0] = None
+        if stdout == subprocess.PIPE:
+            self._pipes[1] = None
+        if stderr == subprocess.PIPE:
+            self._pipes[2] = None
+
+        # Create the child process: set the _proc attribute
+        self._start(args=args, shell=shell, stdin=stdin, stdout=stdout,
+                    stderr=stderr, bufsize=bufsize, **kwargs)
+        self._pid = self._proc.pid
+        self._extra['subprocess'] = self._proc
+
+        if self._loop.get_debug():
+            if isinstance(args, (bytes, str)):
+                program = args
+            else:
+                program = args[0]
+            logger.debug('process %r created: pid %s',
+                         program, self._pid)
+
+        self._loop.create_task(self._connect_pipes(waiter))
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self._closed:
+            info.append('closed')
+        if self._pid is not None:
+            info.append('pid=%s' % self._pid)
+        if self._returncode is not None:
+            info.append('returncode=%s' % self._returncode)
+        elif self._pid is not None:
+            info.append('running')
+        else:
+            info.append('not started')
+
+        stdin = self._pipes.get(0)
+        if stdin is not None:
+            info.append('stdin=%s' % stdin.pipe)
+
+        stdout = self._pipes.get(1)
+        stderr = self._pipes.get(2)
+        if stdout is not None and stderr is stdout:
+            info.append('stdout=stderr=%s' % stdout.pipe)
+        else:
+            if stdout is not None:
+                info.append('stdout=%s' % stdout.pipe)
+            if stderr is not None:
+                info.append('stderr=%s' % stderr.pipe)
+
+        return '<%s>' % ' '.join(info)
+
+    def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs):
+        raise NotImplementedError
+
+    def close(self):
+        if self._closed:
+            return
+        self._closed = True
+
+        for proto in self._pipes.values():
+            if proto is None:
+                continue
+            proto.pipe.close()
+
+        if (self._proc is not None
+        # the child process finished?
+        and self._returncode is None
+        # the child process finished but the transport was not notified yet?
+        and self._proc.poll() is None
+        ):
+            if self._loop.get_debug():
+                logger.warning('Close running child process: kill %r', self)
+
+            try:
+                self._proc.kill()
+            except ProcessLookupError:
+                pass
+
+            # Don't clear the _proc reference yet: _post_init() may still run
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if not self._closed:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self.close()
+
+    def get_pid(self):
+        return self._pid
+
+    def get_returncode(self):
+        return self._returncode
+
+    def get_pipe_transport(self, fd):
+        if fd in self._pipes:
+            return self._pipes[fd].pipe
+        else:
+            return None
+
+    def _check_proc(self):
+        if self._proc is None:
+            raise ProcessLookupError()
+
+    def send_signal(self, signal):
+        self._check_proc()
+        self._proc.send_signal(signal)
+
+    def terminate(self):
+        self._check_proc()
+        self._proc.terminate()
+
+    def kill(self):
+        self._check_proc()
+        self._proc.kill()
+
+    @coroutine
+    def _connect_pipes(self, waiter):
+        try:
+            proc = self._proc
+            loop = self._loop
+
+            if proc.stdin is not None:
+                _, pipe = yield from loop.connect_write_pipe(
+                    lambda: WriteSubprocessPipeProto(self, 0),
+                    proc.stdin)
+                self._pipes[0] = pipe
+
+            if proc.stdout is not None:
+                _, pipe = yield from loop.connect_read_pipe(
+                    lambda: ReadSubprocessPipeProto(self, 1),
+                    proc.stdout)
+                self._pipes[1] = pipe
+
+            if proc.stderr is not None:
+                _, pipe = yield from loop.connect_read_pipe(
+                    lambda: ReadSubprocessPipeProto(self, 2),
+                    proc.stderr)
+                self._pipes[2] = pipe
+
+            assert self._pending_calls is not None
+
+            loop.call_soon(self._protocol.connection_made, self)
+            for callback, data in self._pending_calls:
+                loop.call_soon(callback, *data)
+            self._pending_calls = None
+        except Exception as exc:
+            if waiter is not None and not waiter.cancelled():
+                waiter.set_exception(exc)
+        else:
+            if waiter is not None and not waiter.cancelled():
+                waiter.set_result(None)
+
+    def _call(self, cb, *data):
+        if self._pending_calls is not None:
+            self._pending_calls.append((cb, data))
+        else:
+            self._loop.call_soon(cb, *data)
+
+    def _pipe_connection_lost(self, fd, exc):
+        self._call(self._protocol.pipe_connection_lost, fd, exc)
+        self._try_finish()
+
+    def _pipe_data_received(self, fd, data):
+        self._call(self._protocol.pipe_data_received, fd, data)
+
+    def _process_exited(self, returncode):
+        assert returncode is not None, returncode
+        assert self._returncode is None, self._returncode
+        if self._loop.get_debug():
+            logger.info('%r exited with return code %r',
+                        self, returncode)
+        self._returncode = returncode
+        self._call(self._protocol.process_exited)
+        self._try_finish()
+
+        # wake up futures waiting for wait()
+        for waiter in self._exit_waiters:
+            if not waiter.cancelled():
+                waiter.set_result(returncode)
+        self._exit_waiters = None
+
+    @coroutine
+    def _wait(self):
+        """Wait until the process exit and return the process return code.
+
+        This method is a coroutine."""
+        if self._returncode is not None:
+            return self._returncode
+
+        waiter = futures.Future(loop=self._loop)
+        self._exit_waiters.append(waiter)
+        return (yield from waiter)
+
+    def _try_finish(self):
+        assert not self._finished
+        if self._returncode is None:
+            return
+        if all(p is not None and p.disconnected
+               for p in self._pipes.values()):
+            self._finished = True
+            self._call(self._call_connection_lost, None)
+
+    def _call_connection_lost(self, exc):
+        try:
+            self._protocol.connection_lost(exc)
+        finally:
+            self._loop = None
+            self._proc = None
+            self._protocol = None
+
+
+class WriteSubprocessPipeProto(protocols.BaseProtocol):
+
+    def __init__(self, proc, fd):
+        self.proc = proc
+        self.fd = fd
+        self.pipe = None
+        self.disconnected = False
+
+    def connection_made(self, transport):
+        self.pipe = transport
+
+    def __repr__(self):
+        return ('<%s fd=%s pipe=%r>'
+                % (self.__class__.__name__, self.fd, self.pipe))
+
+    def connection_lost(self, exc):
+        self.disconnected = True
+        self.proc._pipe_connection_lost(self.fd, exc)
+        self.proc = None
+
+    def pause_writing(self):
+        self.proc._protocol.pause_writing()
+
+    def resume_writing(self):
+        self.proc._protocol.resume_writing()
+
+
+class ReadSubprocessPipeProto(WriteSubprocessPipeProto,
+                              protocols.Protocol):
+
+    def data_received(self, data):
+        self.proc._pipe_data_received(self.fd, data)
diff --git a/trollius/constants.py b/trollius/constants.py
new file mode 100644
index 0000000..f9e1232
--- /dev/null
+++ b/trollius/constants.py
@@ -0,0 +1,7 @@
+"""Constants."""
+
+# After the connection is lost, log warnings after this many write()s.
+LOG_THRESHOLD_FOR_CONNLOST_WRITES = 5
+
+# Seconds to wait before retrying accept().
+ACCEPT_RETRY_DELAY = 1
diff --git a/trollius/coroutines.py b/trollius/coroutines.py
new file mode 100644
index 0000000..15475f2
--- /dev/null
+++ b/trollius/coroutines.py
@@ -0,0 +1,301 @@
+__all__ = ['coroutine',
+           'iscoroutinefunction', 'iscoroutine']
+
+import functools
+import inspect
+import opcode
+import os
+import sys
+import traceback
+import types
+
+from . import events
+from . import futures
+from .log import logger
+
+
+_PY35 = sys.version_info >= (3, 5)
+
+
+# Opcode of "yield from" instruction
+_YIELD_FROM = opcode.opmap['YIELD_FROM']
+
+# If you set _DEBUG to true, @coroutine will wrap the resulting
+# generator objects in a CoroWrapper instance (defined below).  That
+# instance will log a message when the generator is never iterated
+# over, which may happen when you forget to use "yield from" with a
+# coroutine call.  Note that the value of the _DEBUG flag is taken
+# when the decorator is used, so to be of any use it must be set
+# before you define your coroutines.  A downside of using this feature
+# is that tracebacks show entries for the CoroWrapper.__next__ method
+# when _DEBUG is true.
+_DEBUG = (not sys.flags.ignore_environment
+          and bool(os.environ.get('PYTHONASYNCIODEBUG')))
+
+
+try:
+    _types_coroutine = types.coroutine
+except AttributeError:
+    _types_coroutine = None
+
+try:
+    _inspect_iscoroutinefunction = inspect.iscoroutinefunction
+except AttributeError:
+    _inspect_iscoroutinefunction = lambda func: False
+
+try:
+    from collections.abc import Coroutine as _CoroutineABC, \
+                                Awaitable as _AwaitableABC
+except ImportError:
+    _CoroutineABC = _AwaitableABC = None
+
+
+# Check for CPython issue #21209
+def has_yield_from_bug():
+    class MyGen:
+        def __init__(self):
+            self.send_args = None
+        def __iter__(self):
+            return self
+        def __next__(self):
+            return 42
+        def send(self, *what):
+            self.send_args = what
+            return None
+    def yield_from_gen(gen):
+        yield from gen
+    value = (1, 2, 3)
+    gen = MyGen()
+    coro = yield_from_gen(gen)
+    next(coro)
+    coro.send(value)
+    return gen.send_args != (value,)
+_YIELD_FROM_BUG = has_yield_from_bug()
+del has_yield_from_bug
+
+
+def debug_wrapper(gen):
+    # This function is called from 'sys.set_coroutine_wrapper'.
+    # We only wrap here coroutines defined via 'async def' syntax.
+    # Generator-based coroutines are wrapped in @coroutine
+    # decorator.
+    return CoroWrapper(gen, None)
+
+
+class CoroWrapper:
+    # Wrapper for coroutine object in _DEBUG mode.
+
+    def __init__(self, gen, func=None):
+        assert inspect.isgenerator(gen) or inspect.iscoroutine(gen), gen
+        self.gen = gen
+        self.func = func # Used to unwrap @coroutine decorator
+        self._source_traceback = traceback.extract_stack(sys._getframe(1))
+        self.__name__ = getattr(gen, '__name__', None)
+        self.__qualname__ = getattr(gen, '__qualname__', None)
+
+    def __repr__(self):
+        coro_repr = _format_coroutine(self)
+        if self._source_traceback:
+            frame = self._source_traceback[-1]
+            coro_repr += ', created at %s:%s' % (frame[0], frame[1])
+        return '<%s %s>' % (self.__class__.__name__, coro_repr)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        return self.gen.send(None)
+
+    if _YIELD_FROM_BUG:
+        # For for CPython issue #21209: using "yield from" and a custom
+        # generator, generator.send(tuple) unpacks the tuple instead of passing
+        # the tuple unchanged. Check if the caller is a generator using "yield
+        # from" to decide if the parameter should be unpacked or not.
+        def send(self, *value):
+            frame = sys._getframe()
+            caller = frame.f_back
+            assert caller.f_lasti >= 0
+            if caller.f_code.co_code[caller.f_lasti] != _YIELD_FROM:
+                value = value[0]
+            return self.gen.send(value)
+    else:
+        def send(self, value):
+            return self.gen.send(value)
+
+    def throw(self, exc):
+        return self.gen.throw(exc)
+
+    def close(self):
+        return self.gen.close()
+
+    @property
+    def gi_frame(self):
+        return self.gen.gi_frame
+
+    @property
+    def gi_running(self):
+        return self.gen.gi_running
+
+    @property
+    def gi_code(self):
+        return self.gen.gi_code
+
+    if _PY35:
+
+        __await__ = __iter__ # make compatible with 'await' expression
+
+        @property
+        def gi_yieldfrom(self):
+            return self.gen.gi_yieldfrom
+
+        @property
+        def cr_await(self):
+            return self.gen.cr_await
+
+        @property
+        def cr_running(self):
+            return self.gen.cr_running
+
+        @property
+        def cr_code(self):
+            return self.gen.cr_code
+
+        @property
+        def cr_frame(self):
+            return self.gen.cr_frame
+
+    def __del__(self):
+        # Be careful accessing self.gen.frame -- self.gen might not exist.
+        gen = getattr(self, 'gen', None)
+        frame = getattr(gen, 'gi_frame', None)
+        if frame is None:
+            frame = getattr(gen, 'cr_frame', None)
+        if frame is not None and frame.f_lasti == -1:
+            msg = '%r was never yielded from' % self
+            tb = getattr(self, '_source_traceback', ())
+            if tb:
+                tb = ''.join(traceback.format_list(tb))
+                msg += ('\nCoroutine object created at '
+                        '(most recent call last):\n')
+                msg += tb.rstrip()
+            logger.error(msg)
+
+
+def coroutine(func):
+    """Decorator to mark coroutines.
+
+    If the coroutine is not yielded from before it is destroyed,
+    an error message is logged.
+    """
+    if _inspect_iscoroutinefunction(func):
+        # In Python 3.5 that's all we need to do for coroutines
+        # defiend with "async def".
+        # Wrapping in CoroWrapper will happen via
+        # 'sys.set_coroutine_wrapper' function.
+        return func
+
+    if inspect.isgeneratorfunction(func):
+        coro = func
+    else:
+        @functools.wraps(func)
+        def coro(*args, **kw):
+            res = func(*args, **kw)
+            if isinstance(res, futures.Future) or inspect.isgenerator(res):
+                res = yield from res
+            elif _AwaitableABC is not None:
+                # If 'func' returns an Awaitable (new in 3.5) we
+                # want to run it.
+                try:
+                    await_meth = res.__await__
+                except AttributeError:
+                    pass
+                else:
+                    if isinstance(res, _AwaitableABC):
+                        res = yield from await_meth()
+            return res
+
+    if not _DEBUG:
+        if _types_coroutine is None:
+            wrapper = coro
+        else:
+            wrapper = _types_coroutine(coro)
+    else:
+        @functools.wraps(func)
+        def wrapper(*args, **kwds):
+            w = CoroWrapper(coro(*args, **kwds), func=func)
+            if w._source_traceback:
+                del w._source_traceback[-1]
+            # Python < 3.5 does not implement __qualname__
+            # on generator objects, so we set it manually.
+            # We use getattr as some callables (such as
+            # functools.partial may lack __qualname__).
+            w.__name__ = getattr(func, '__name__', None)
+            w.__qualname__ = getattr(func, '__qualname__', None)
+            return w
+
+    wrapper._is_coroutine = True  # For iscoroutinefunction().
+    return wrapper
+
+
+def iscoroutinefunction(func):
+    """Return True if func is a decorated coroutine function."""
+    return (getattr(func, '_is_coroutine', False) or
+            _inspect_iscoroutinefunction(func))
+
+
+_COROUTINE_TYPES = (types.GeneratorType, CoroWrapper)
+if _CoroutineABC is not None:
+    _COROUTINE_TYPES += (_CoroutineABC,)
+
+
+def iscoroutine(obj):
+    """Return True if obj is a coroutine object."""
+    return isinstance(obj, _COROUTINE_TYPES)
+
+
+def _format_coroutine(coro):
+    assert iscoroutine(coro)
+
+    coro_name = None
+    if isinstance(coro, CoroWrapper):
+        func = coro.func
+        coro_name = coro.__qualname__
+        if coro_name is not None:
+            coro_name = '{}()'.format(coro_name)
+    else:
+        func = coro
+
+    if coro_name is None:
+        coro_name = events._format_callback(func, ())
+
+    try:
+        coro_code = coro.gi_code
+    except AttributeError:
+        coro_code = coro.cr_code
+
+    try:
+        coro_frame = coro.gi_frame
+    except AttributeError:
+        coro_frame = coro.cr_frame
+
+    filename = coro_code.co_filename
+    if (isinstance(coro, CoroWrapper)
+    and not inspect.isgeneratorfunction(coro.func)
+    and coro.func is not None):
+        filename, lineno = events._get_function_source(coro.func)
+        if coro_frame is None:
+            coro_repr = ('%s done, defined at %s:%s'
+                         % (coro_name, filename, lineno))
+        else:
+            coro_repr = ('%s running, defined at %s:%s'
+                         % (coro_name, filename, lineno))
+    elif coro_frame is not None:
+        lineno = coro_frame.f_lineno
+        coro_repr = ('%s running at %s:%s'
+                     % (coro_name, filename, lineno))
+    else:
+        lineno = coro_code.co_firstlineno
+        coro_repr = ('%s done, defined at %s:%s'
+                     % (coro_name, filename, lineno))
+
+    return coro_repr
diff --git a/trollius/events.py b/trollius/events.py
new file mode 100644
index 0000000..496075b
--- /dev/null
+++ b/trollius/events.py
@@ -0,0 +1,611 @@
+"""Event loop and event loop policy."""
+
+__all__ = ['AbstractEventLoopPolicy',
+           'AbstractEventLoop', 'AbstractServer',
+           'Handle', 'TimerHandle',
+           'get_event_loop_policy', 'set_event_loop_policy',
+           'get_event_loop', 'set_event_loop', 'new_event_loop',
+           'get_child_watcher', 'set_child_watcher',
+           ]
+
+import functools
+import inspect
+import reprlib
+import socket
+import subprocess
+import sys
+import threading
+import traceback
+
+
+_PY34 = sys.version_info >= (3, 4)
+
+
+def _get_function_source(func):
+    if _PY34:
+        func = inspect.unwrap(func)
+    elif hasattr(func, '__wrapped__'):
+        func = func.__wrapped__
+    if inspect.isfunction(func):
+        code = func.__code__
+        return (code.co_filename, code.co_firstlineno)
+    if isinstance(func, functools.partial):
+        return _get_function_source(func.func)
+    if _PY34 and isinstance(func, functools.partialmethod):
+        return _get_function_source(func.func)
+    return None
+
+
+def _format_args(args):
+    """Format function arguments.
+
+    Special case for a single parameter: ('hello',) is formatted as ('hello').
+    """
+    # use reprlib to limit the length of the output
+    args_repr = reprlib.repr(args)
+    if len(args) == 1 and args_repr.endswith(',)'):
+        args_repr = args_repr[:-2] + ')'
+    return args_repr
+
+
+def _format_callback(func, args, suffix=''):
+    if isinstance(func, functools.partial):
+        if args is not None:
+            suffix = _format_args(args) + suffix
+        return _format_callback(func.func, func.args, suffix)
+
+    if hasattr(func, '__qualname__'):
+        func_repr = getattr(func, '__qualname__')
+    elif hasattr(func, '__name__'):
+        func_repr = getattr(func, '__name__')
+    else:
+        func_repr = repr(func)
+
+    if args is not None:
+        func_repr += _format_args(args)
+    if suffix:
+        func_repr += suffix
+    return func_repr
+
+def _format_callback_source(func, args):
+    func_repr = _format_callback(func, args)
+    source = _get_function_source(func)
+    if source:
+        func_repr += ' at %s:%s' % source
+    return func_repr
+
+
+class Handle:
+    """Object returned by callback registration methods."""
+
+    __slots__ = ('_callback', '_args', '_cancelled', '_loop',
+                 '_source_traceback', '_repr', '__weakref__')
+
+    def __init__(self, callback, args, loop):
+        assert not isinstance(callback, Handle), 'A Handle is not a callback'
+        self._loop = loop
+        self._callback = callback
+        self._args = args
+        self._cancelled = False
+        self._repr = None
+        if self._loop.get_debug():
+            self._source_traceback = traceback.extract_stack(sys._getframe(1))
+        else:
+            self._source_traceback = None
+
+    def _repr_info(self):
+        info = [self.__class__.__name__]
+        if self._cancelled:
+            info.append('cancelled')
+        if self._callback is not None:
+            info.append(_format_callback_source(self._callback, self._args))
+        if self._source_traceback:
+            frame = self._source_traceback[-1]
+            info.append('created at %s:%s' % (frame[0], frame[1]))
+        return info
+
+    def __repr__(self):
+        if self._repr is not None:
+            return self._repr
+        info = self._repr_info()
+        return '<%s>' % ' '.join(info)
+
+    def cancel(self):
+        if not self._cancelled:
+            self._cancelled = True
+            if self._loop.get_debug():
+                # Keep a representation in debug mode to keep callback and
+                # parameters. For example, to log the warning
+                # "Executing <Handle...> took 2.5 second"
+                self._repr = repr(self)
+            self._callback = None
+            self._args = None
+
+    def _run(self):
+        try:
+            self._callback(*self._args)
+        except Exception as exc:
+            cb = _format_callback_source(self._callback, self._args)
+            msg = 'Exception in callback {}'.format(cb)
+            context = {
+                'message': msg,
+                'exception': exc,
+                'handle': self,
+            }
+            if self._source_traceback:
+                context['source_traceback'] = self._source_traceback
+            self._loop.call_exception_handler(context)
+        self = None  # Needed to break cycles when an exception occurs.
+
+
+class TimerHandle(Handle):
+    """Object returned by timed callback registration methods."""
+
+    __slots__ = ['_scheduled', '_when']
+
+    def __init__(self, when, callback, args, loop):
+        assert when is not None
+        super().__init__(callback, args, loop)
+        if self._source_traceback:
+            del self._source_traceback[-1]
+        self._when = when
+        self._scheduled = False
+
+    def _repr_info(self):
+        info = super()._repr_info()
+        pos = 2 if self._cancelled else 1
+        info.insert(pos, 'when=%s' % self._when)
+        return info
+
+    def __hash__(self):
+        return hash(self._when)
+
+    def __lt__(self, other):
+        return self._when < other._when
+
+    def __le__(self, other):
+        if self._when < other._when:
+            return True
+        return self.__eq__(other)
+
+    def __gt__(self, other):
+        return self._when > other._when
+
+    def __ge__(self, other):
+        if self._when > other._when:
+            return True
+        return self.__eq__(other)
+
+    def __eq__(self, other):
+        if isinstance(other, TimerHandle):
+            return (self._when == other._when and
+                    self._callback == other._callback and
+                    self._args == other._args and
+                    self._cancelled == other._cancelled)
+        return NotImplemented
+
+    def __ne__(self, other):
+        equal = self.__eq__(other)
+        return NotImplemented if equal is NotImplemented else not equal
+
+    def cancel(self):
+        if not self._cancelled:
+            self._loop._timer_handle_cancelled(self)
+        super().cancel()
+
+
+class AbstractServer:
+    """Abstract server returned by create_server()."""
+
+    def close(self):
+        """Stop serving.  This leaves existing connections open."""
+        return NotImplemented
+
+    def wait_closed(self):
+        """Coroutine to wait until service is closed."""
+        return NotImplemented
+
+
+class AbstractEventLoop:
+    """Abstract event loop."""
+
+    # Running and stopping the event loop.
+
+    def run_forever(self):
+        """Run the event loop until stop() is called."""
+        raise NotImplementedError
+
+    def run_until_complete(self, future):
+        """Run the event loop until a Future is done.
+
+        Return the Future's result, or raise its exception.
+        """
+        raise NotImplementedError
+
+    def stop(self):
+        """Stop the event loop as soon as reasonable.
+
+        Exactly how soon that is may depend on the implementation, but
+        no more I/O callbacks should be scheduled.
+        """
+        raise NotImplementedError
+
+    def is_running(self):
+        """Return whether the event loop is currently running."""
+        raise NotImplementedError
+
+    def is_closed(self):
+        """Returns True if the event loop was closed."""
+        raise NotImplementedError
+
+    def close(self):
+        """Close the loop.
+
+        The loop should not be running.
+
+        This is idempotent and irreversible.
+
+        No other methods should be called after this one.
+        """
+        raise NotImplementedError
+
+    # Methods scheduling callbacks.  All these return Handles.
+
+    def _timer_handle_cancelled(self, handle):
+        """Notification that a TimerHandle has been cancelled."""
+        raise NotImplementedError
+
+    def call_soon(self, callback, *args):
+        return self.call_later(0, callback, *args)
+
+    def call_later(self, delay, callback, *args):
+        raise NotImplementedError
+
+    def call_at(self, when, callback, *args):
+        raise NotImplementedError
+
+    def time(self):
+        raise NotImplementedError
+
+    # Method scheduling a coroutine object: create a task.
+
+    def create_task(self, coro):
+        raise NotImplementedError
+
+    # Methods for interacting with threads.
+
+    def call_soon_threadsafe(self, callback, *args):
+        raise NotImplementedError
+
+    def run_in_executor(self, executor, func, *args):
+        raise NotImplementedError
+
+    def set_default_executor(self, executor):
+        raise NotImplementedError
+
+    # Network I/O methods returning Futures.
+
+    def getaddrinfo(self, host, port, *, family=0, type=0, proto=0, flags=0):
+        raise NotImplementedError
+
+    def getnameinfo(self, sockaddr, flags=0):
+        raise NotImplementedError
+
+    def create_connection(self, protocol_factory, host=None, port=None, *,
+                          ssl=None, family=0, proto=0, flags=0, sock=None,
+                          local_addr=None, server_hostname=None):
+        raise NotImplementedError
+
+    def create_server(self, protocol_factory, host=None, port=None, *,
+                      family=socket.AF_UNSPEC, flags=socket.AI_PASSIVE,
+                      sock=None, backlog=100, ssl=None, reuse_address=None):
+        """A coroutine which creates a TCP server bound to host and port.
+
+        The return value is a Server object which can be used to stop
+        the service.
+
+        If host is an empty string or None all interfaces are assumed
+        and a list of multiple sockets will be returned (most likely
+        one for IPv4 and another one for IPv6).
+
+        family can be set to either AF_INET or AF_INET6 to force the
+        socket to use IPv4 or IPv6. If not set it will be determined
+        from host (defaults to AF_UNSPEC).
+
+        flags is a bitmask for getaddrinfo().
+
+        sock can optionally be specified in order to use a preexisting
+        socket object.
+
+        backlog is the maximum number of queued connections passed to
+        listen() (defaults to 100).
+
+        ssl can be set to an SSLContext to enable SSL over the
+        accepted connections.
+
+        reuse_address tells the kernel to reuse a local socket in
+        TIME_WAIT state, without waiting for its natural timeout to
+        expire. If not specified will automatically be set to True on
+        UNIX.
+        """
+        raise NotImplementedError
+
+    def create_unix_connection(self, protocol_factory, path, *,
+                               ssl=None, sock=None,
+                               server_hostname=None):
+        raise NotImplementedError
+
+    def create_unix_server(self, protocol_factory, path, *,
+                           sock=None, backlog=100, ssl=None):
+        """A coroutine which creates a UNIX Domain Socket server.
+
+        The return value is a Server object, which can be used to stop
+        the service.
+
+        path is a str, representing a file systsem path to bind the
+        server socket to.
+
+        sock can optionally be specified in order to use a preexisting
+        socket object.
+
+        backlog is the maximum number of queued connections passed to
+        listen() (defaults to 100).
+
+        ssl can be set to an SSLContext to enable SSL over the
+        accepted connections.
+        """
+        raise NotImplementedError
+
+    def create_datagram_endpoint(self, protocol_factory,
+                                 local_addr=None, remote_addr=None, *,
+                                 family=0, proto=0, flags=0):
+        raise NotImplementedError
+
+    # Pipes and subprocesses.
+
+    def connect_read_pipe(self, protocol_factory, pipe):
+        """Register read pipe in event loop. Set the pipe to non-blocking mode.
+
+        protocol_factory should instantiate object with Protocol interface.
+        pipe is a file-like object.
+        Return pair (transport, protocol), where transport supports the
+        ReadTransport interface."""
+        # The reason to accept file-like object instead of just file descriptor
+        # is: we need to own pipe and close it at transport finishing
+        # Can got complicated errors if pass f.fileno(),
+        # close fd in pipe transport then close f and vise versa.
+        raise NotImplementedError
+
+    def connect_write_pipe(self, protocol_factory, pipe):
+        """Register write pipe in event loop.
+
+        protocol_factory should instantiate object with BaseProtocol interface.
+        Pipe is file-like object already switched to nonblocking.
+        Return pair (transport, protocol), where transport support
+        WriteTransport interface."""
+        # The reason to accept file-like object instead of just file descriptor
+        # is: we need to own pipe and close it at transport finishing
+        # Can got complicated errors if pass f.fileno(),
+        # close fd in pipe transport then close f and vise versa.
+        raise NotImplementedError
+
+    def subprocess_shell(self, protocol_factory, cmd, *, stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                         **kwargs):
+        raise NotImplementedError
+
+    def subprocess_exec(self, protocol_factory, *args, stdin=subprocess.PIPE,
+                        stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                        **kwargs):
+        raise NotImplementedError
+
+    # Ready-based callback registration methods.
+    # The add_*() methods return None.
+    # The remove_*() methods return True if something was removed,
+    # False if there was nothing to delete.
+
+    def add_reader(self, fd, callback, *args):
+        raise NotImplementedError
+
+    def remove_reader(self, fd):
+        raise NotImplementedError
+
+    def add_writer(self, fd, callback, *args):
+        raise NotImplementedError
+
+    def remove_writer(self, fd):
+        raise NotImplementedError
+
+    # Completion based I/O methods returning Futures.
+
+    def sock_recv(self, sock, nbytes):
+        raise NotImplementedError
+
+    def sock_sendall(self, sock, data):
+        raise NotImplementedError
+
+    def sock_connect(self, sock, address):
+        raise NotImplementedError
+
+    def sock_accept(self, sock):
+        raise NotImplementedError
+
+    # Signal handling.
+
+    def add_signal_handler(self, sig, callback, *args):
+        raise NotImplementedError
+
+    def remove_signal_handler(self, sig):
+        raise NotImplementedError
+
+    # Task factory.
+
+    def set_task_factory(self, factory):
+        raise NotImplementedError
+
+    def get_task_factory(self):
+        raise NotImplementedError
+
+    # Error handlers.
+
+    def set_exception_handler(self, handler):
+        raise NotImplementedError
+
+    def default_exception_handler(self, context):
+        raise NotImplementedError
+
+    def call_exception_handler(self, context):
+        raise NotImplementedError
+
+    # Debug flag management.
+
+    def get_debug(self):
+        raise NotImplementedError
+
+    def set_debug(self, enabled):
+        raise NotImplementedError
+
+
+class AbstractEventLoopPolicy:
+    """Abstract policy for accessing the event loop."""
+
+    def get_event_loop(self):
+        """Get the event loop for the current context.
+
+        Returns an event loop object implementing the BaseEventLoop interface,
+        or raises an exception in case no event loop has been set for the
+        current context and the current policy does not specify to create one.
+
+        It should never return None."""
+        raise NotImplementedError
+
+    def set_event_loop(self, loop):
+        """Set the event loop for the current context to loop."""
+        raise NotImplementedError
+
+    def new_event_loop(self):
+        """Create and return a new event loop object according to this
+        policy's rules. If there's need to set this loop as the event loop for
+        the current context, set_event_loop must be called explicitly."""
+        raise NotImplementedError
+
+    # Child processes handling (Unix only).
+
+    def get_child_watcher(self):
+        "Get the watcher for child processes."
+        raise NotImplementedError
+
+    def set_child_watcher(self, watcher):
+        """Set the watcher for child processes."""
+        raise NotImplementedError
+
+
+class BaseDefaultEventLoopPolicy(AbstractEventLoopPolicy):
+    """Default policy implementation for accessing the event loop.
+
+    In this policy, each thread has its own event loop.  However, we
+    only automatically create an event loop by default for the main
+    thread; other threads by default have no event loop.
+
+    Other policies may have different rules (e.g. a single global
+    event loop, or automatically creating an event loop per thread, or
+    using some other notion of context to which an event loop is
+    associated).
+    """
+
+    _loop_factory = None
+
+    class _Local(threading.local):
+        _loop = None
+        _set_called = False
+
+    def __init__(self):
+        self._local = self._Local()
+
+    def get_event_loop(self):
+        """Get the event loop.
+
+        This may be None or an instance of EventLoop.
+        """
+        if (self._local._loop is None and
+            not self._local._set_called and
+            isinstance(threading.current_thread(), threading._MainThread)):
+            self.set_event_loop(self.new_event_loop())
+        if self._local._loop is None:
+            raise RuntimeError('There is no current event loop in thread %r.'
+                               % threading.current_thread().name)
+        return self._local._loop
+
+    def set_event_loop(self, loop):
+        """Set the event loop."""
+        self._local._set_called = True
+        assert loop is None or isinstance(loop, AbstractEventLoop)
+        self._local._loop = loop
+
+    def new_event_loop(self):
+        """Create a new event loop.
+
+        You must call set_event_loop() to make this the current event
+        loop.
+        """
+        return self._loop_factory()
+
+
+# Event loop policy.  The policy itself is always global, even if the
+# policy's rules say that there is an event loop per thread (or other
+# notion of context).  The default policy is installed by the first
+# call to get_event_loop_policy().
+_event_loop_policy = None
+
+# Lock for protecting the on-the-fly creation of the event loop policy.
+_lock = threading.Lock()
+
+
+def _init_event_loop_policy():
+    global _event_loop_policy
+    with _lock:
+        if _event_loop_policy is None:  # pragma: no branch
+            from . import DefaultEventLoopPolicy
+            _event_loop_policy = DefaultEventLoopPolicy()
+
+
+def get_event_loop_policy():
+    """Get the current event loop policy."""
+    if _event_loop_policy is None:
+        _init_event_loop_policy()
+    return _event_loop_policy
+
+
+def set_event_loop_policy(policy):
+    """Set the current event loop policy.
+
+    If policy is None, the default policy is restored."""
+    global _event_loop_policy
+    assert policy is None or isinstance(policy, AbstractEventLoopPolicy)
+    _event_loop_policy = policy
+
+
+def get_event_loop():
+    """Equivalent to calling get_event_loop_policy().get_event_loop()."""
+    return get_event_loop_policy().get_event_loop()
+
+
+def set_event_loop(loop):
+    """Equivalent to calling get_event_loop_policy().set_event_loop(loop)."""
+    get_event_loop_policy().set_event_loop(loop)
+
+
+def new_event_loop():
+    """Equivalent to calling get_event_loop_policy().new_event_loop()."""
+    return get_event_loop_policy().new_event_loop()
+
+
+def get_child_watcher():
+    """Equivalent to calling get_event_loop_policy().get_child_watcher()."""
+    return get_event_loop_policy().get_child_watcher()
+
+
+def set_child_watcher(watcher):
+    """Equivalent to calling
+    get_event_loop_policy().set_child_watcher(watcher)."""
+    return get_event_loop_policy().set_child_watcher(watcher)
diff --git a/trollius/futures.py b/trollius/futures.py
new file mode 100644
index 0000000..d06828a
--- /dev/null
+++ b/trollius/futures.py
@@ -0,0 +1,413 @@
+"""A Future class similar to the one in PEP 3148."""
+
+__all__ = ['CancelledError', 'TimeoutError',
+           'InvalidStateError',
+           'Future', 'wrap_future',
+           ]
+
+import concurrent.futures._base
+import logging
+import reprlib
+import sys
+import traceback
+
+from . import events
+
+# States for Future.
+_PENDING = 'PENDING'
+_CANCELLED = 'CANCELLED'
+_FINISHED = 'FINISHED'
+
+_PY34 = sys.version_info >= (3, 4)
+_PY35 = sys.version_info >= (3, 5)
+
+Error = concurrent.futures._base.Error
+CancelledError = concurrent.futures.CancelledError
+TimeoutError = concurrent.futures.TimeoutError
+
+STACK_DEBUG = logging.DEBUG - 1  # heavy-duty debugging
+
+
+class InvalidStateError(Error):
+    """The operation is not allowed in this state."""
+
+
+class _TracebackLogger:
+    """Helper to log a traceback upon destruction if not cleared.
+
+    This solves a nasty problem with Futures and Tasks that have an
+    exception set: if nobody asks for the exception, the exception is
+    never logged.  This violates the Zen of Python: 'Errors should
+    never pass silently.  Unless explicitly silenced.'
+
+    However, we don't want to log the exception as soon as
+    set_exception() is called: if the calling code is written
+    properly, it will get the exception and handle it properly.  But
+    we *do* want to log it if result() or exception() was never called
+    -- otherwise developers waste a lot of time wondering why their
+    buggy code fails silently.
+
+    An earlier attempt added a __del__() method to the Future class
+    itself, but this backfired because the presence of __del__()
+    prevents garbage collection from breaking cycles.  A way out of
+    this catch-22 is to avoid having a __del__() method on the Future
+    class itself, but instead to have a reference to a helper object
+    with a __del__() method that logs the traceback, where we ensure
+    that the helper object doesn't participate in cycles, and only the
+    Future has a reference to it.
+
+    The helper object is added when set_exception() is called.  When
+    the Future is collected, and the helper is present, the helper
+    object is also collected, and its __del__() method will log the
+    traceback.  When the Future's result() or exception() method is
+    called (and a helper object is present), it removes the helper
+    object, after calling its clear() method to prevent it from
+    logging.
+
+    One downside is that we do a fair amount of work to extract the
+    traceback from the exception, even when it is never logged.  It
+    would seem cheaper to just store the exception object, but that
+    references the traceback, which references stack frames, which may
+    reference the Future, which references the _TracebackLogger, and
+    then the _TracebackLogger would be included in a cycle, which is
+    what we're trying to avoid!  As an optimization, we don't
+    immediately format the exception; we only do the work when
+    activate() is called, which call is delayed until after all the
+    Future's callbacks have run.  Since usually a Future has at least
+    one callback (typically set by 'yield from') and usually that
+    callback extracts the callback, thereby removing the need to
+    format the exception.
+
+    PS. I don't claim credit for this solution.  I first heard of it
+    in a discussion about closing files when they are collected.
+    """
+
+    __slots__ = ('loop', 'source_traceback', 'exc', 'tb')
+
+    def __init__(self, future, exc):
+        self.loop = future._loop
+        self.source_traceback = future._source_traceback
+        self.exc = exc
+        self.tb = None
+
+    def activate(self):
+        exc = self.exc
+        if exc is not None:
+            self.exc = None
+            self.tb = traceback.format_exception(exc.__class__, exc,
+                                                 exc.__traceback__)
+
+    def clear(self):
+        self.exc = None
+        self.tb = None
+
+    def __del__(self):
+        if self.tb:
+            msg = 'Future/Task exception was never retrieved\n'
+            if self.source_traceback:
+                src = ''.join(traceback.format_list(self.source_traceback))
+                msg += 'Future/Task created at (most recent call last):\n'
+                msg += '%s\n' % src.rstrip()
+            msg += ''.join(self.tb).rstrip()
+            self.loop.call_exception_handler({'message': msg})
+
+
+class Future:
+    """This class is *almost* compatible with concurrent.futures.Future.
+
+    Differences:
+
+    - result() and exception() do not take a timeout argument and
+      raise an exception when the future isn't done yet.
+
+    - Callbacks registered with add_done_callback() are always called
+      via the event loop's call_soon_threadsafe().
+
+    - This class is not compatible with the wait() and as_completed()
+      methods in the concurrent.futures package.
+
+    (In Python 3.4 or later we may be able to unify the implementations.)
+    """
+
+    # Class variables serving as defaults for instance variables.
+    _state = _PENDING
+    _result = None
+    _exception = None
+    _loop = None
+    _source_traceback = None
+
+    _blocking = False  # proper use of future (yield vs yield from)
+
+    _log_traceback = False   # Used for Python 3.4 and later
+    _tb_logger = None        # Used for Python 3.3 only
+
+    def __init__(self, *, loop=None):
+        """Initialize the future.
+
+        The optional event_loop argument allows to explicitly set the event
+        loop object used by the future. If it's not provided, the future uses
+        the default event loop.
+        """
+        if loop is None:
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
+        self._callbacks = []
+        if self._loop.get_debug():
+            self._source_traceback = traceback.extract_stack(sys._getframe(1))
+
+    def _format_callbacks(self):
+        cb = self._callbacks
+        size = len(cb)
+        if not size:
+            cb = ''
+
+        def format_cb(callback):
+            return events._format_callback_source(callback, ())
+
+        if size == 1:
+            cb = format_cb(cb[0])
+        elif size == 2:
+            cb = '{}, {}'.format(format_cb(cb[0]), format_cb(cb[1]))
+        elif size > 2:
+            cb = '{}, <{} more>, {}'.format(format_cb(cb[0]),
+                                            size-2,
+                                            format_cb(cb[-1]))
+        return 'cb=[%s]' % cb
+
+    def _repr_info(self):
+        info = [self._state.lower()]
+        if self._state == _FINISHED:
+            if self._exception is not None:
+                info.append('exception={!r}'.format(self._exception))
+            else:
+                # use reprlib to limit the length of the output, especially
+                # for very long strings
+                result = reprlib.repr(self._result)
+                info.append('result={}'.format(result))
+        if self._callbacks:
+            info.append(self._format_callbacks())
+        if self._source_traceback:
+            frame = self._source_traceback[-1]
+            info.append('created at %s:%s' % (frame[0], frame[1]))
+        return info
+
+    def __repr__(self):
+        info = self._repr_info()
+        return '<%s %s>' % (self.__class__.__name__, ' '.join(info))
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if _PY34:
+        def __del__(self):
+            if not self._log_traceback:
+                # set_exception() was not called, or result() or exception()
+                # has consumed the exception
+                return
+            exc = self._exception
+            context = {
+                'message': ('%s exception was never retrieved'
+                            % self.__class__.__name__),
+                'exception': exc,
+                'future': self,
+            }
+            if self._source_traceback:
+                context['source_traceback'] = self._source_traceback
+            self._loop.call_exception_handler(context)
+
+    def cancel(self):
+        """Cancel the future and schedule callbacks.
+
+        If the future is already done or cancelled, return False.  Otherwise,
+        change the future's state to cancelled, schedule the callbacks and
+        return True.
+        """
+        if self._state != _PENDING:
+            return False
+        self._state = _CANCELLED
+        self._schedule_callbacks()
+        return True
+
+    def _schedule_callbacks(self):
+        """Internal: Ask the event loop to call all callbacks.
+
+        The callbacks are scheduled to be called as soon as possible. Also
+        clears the callback list.
+        """
+        callbacks = self._callbacks[:]
+        if not callbacks:
+            return
+
+        self._callbacks[:] = []
+        for callback in callbacks:
+            self._loop.call_soon(callback, self)
+
+    def cancelled(self):
+        """Return True if the future was cancelled."""
+        return self._state == _CANCELLED
+
+    # Don't implement running(); see http://bugs.python.org/issue18699
+
+    def done(self):
+        """Return True if the future is done.
+
+        Done means either that a result / exception are available, or that the
+        future was cancelled.
+        """
+        return self._state != _PENDING
+
+    def result(self):
+        """Return the result this future represents.
+
+        If the future has been cancelled, raises CancelledError.  If the
+        future's result isn't yet available, raises InvalidStateError.  If
+        the future is done and has an exception set, this exception is raised.
+        """
+        if self._state == _CANCELLED:
+            raise CancelledError
+        if self._state != _FINISHED:
+            raise InvalidStateError('Result is not ready.')
+        self._log_traceback = False
+        if self._tb_logger is not None:
+            self._tb_logger.clear()
+            self._tb_logger = None
+        if self._exception is not None:
+            raise self._exception
+        return self._result
+
+    def exception(self):
+        """Return the exception that was set on this future.
+
+        The exception (or None if no exception was set) is returned only if
+        the future is done.  If the future has been cancelled, raises
+        CancelledError.  If the future isn't done yet, raises
+        InvalidStateError.
+        """
+        if self._state == _CANCELLED:
+            raise CancelledError
+        if self._state != _FINISHED:
+            raise InvalidStateError('Exception is not set.')
+        self._log_traceback = False
+        if self._tb_logger is not None:
+            self._tb_logger.clear()
+            self._tb_logger = None
+        return self._exception
+
+    def add_done_callback(self, fn):
+        """Add a callback to be run when the future becomes done.
+
+        The callback is called with a single argument - the future object. If
+        the future is already done when this is called, the callback is
+        scheduled with call_soon.
+        """
+        if self._state != _PENDING:
+            self._loop.call_soon(fn, self)
+        else:
+            self._callbacks.append(fn)
+
+    # New method not in PEP 3148.
+
+    def remove_done_callback(self, fn):
+        """Remove all instances of a callback from the "call when done" list.
+
+        Returns the number of callbacks removed.
+        """
+        filtered_callbacks = [f for f in self._callbacks if f != fn]
+        removed_count = len(self._callbacks) - len(filtered_callbacks)
+        if removed_count:
+            self._callbacks[:] = filtered_callbacks
+        return removed_count
+
+    # So-called internal methods (note: no set_running_or_notify_cancel()).
+
+    def _set_result_unless_cancelled(self, result):
+        """Helper setting the result only if the future was not cancelled."""
+        if self.cancelled():
+            return
+        self.set_result(result)
+
+    def set_result(self, result):
+        """Mark the future done and set its result.
+
+        If the future is already done when this method is called, raises
+        InvalidStateError.
+        """
+        if self._state != _PENDING:
+            raise InvalidStateError('{}: {!r}'.format(self._state, self))
+        self._result = result
+        self._state = _FINISHED
+        self._schedule_callbacks()
+
+    def set_exception(self, exception):
+        """Mark the future done and set an exception.
+
+        If the future is already done when this method is called, raises
+        InvalidStateError.
+        """
+        if self._state != _PENDING:
+            raise InvalidStateError('{}: {!r}'.format(self._state, self))
+        if isinstance(exception, type):
+            exception = exception()
+        self._exception = exception
+        self._state = _FINISHED
+        self._schedule_callbacks()
+        if _PY34:
+            self._log_traceback = True
+        else:
+            self._tb_logger = _TracebackLogger(self, exception)
+            # Arrange for the logger to be activated after all callbacks
+            # have had a chance to call result() or exception().
+            self._loop.call_soon(self._tb_logger.activate)
+
+    # Truly internal methods.
+
+    def _copy_state(self, other):
+        """Internal helper to copy state from another Future.
+
+        The other Future may be a concurrent.futures.Future.
+        """
+        assert other.done()
+        if self.cancelled():
+            return
+        assert not self.done()
+        if other.cancelled():
+            self.cancel()
+        else:
+            exception = other.exception()
+            if exception is not None:
+                self.set_exception(exception)
+            else:
+                result = other.result()
+                self.set_result(result)
+
+    def __iter__(self):
+        if not self.done():
+            self._blocking = True
+            yield self  # This tells Task to wait for completion.
+        assert self.done(), "yield from wasn't used with future"
+        return self.result()  # May raise too.
+
+    if _PY35:
+        __await__ = __iter__ # make compatible with 'await' expression
+
+
+def wrap_future(fut, *, loop=None):
+    """Wrap concurrent.futures.Future object."""
+    if isinstance(fut, Future):
+        return fut
+    assert isinstance(fut, concurrent.futures.Future), \
+        'concurrent.futures.Future is expected, got {!r}'.format(fut)
+    if loop is None:
+        loop = events.get_event_loop()
+    new_future = Future(loop=loop)
+
+    def _check_cancel_other(f):
+        if f.cancelled():
+            fut.cancel()
+
+    new_future.add_done_callback(_check_cancel_other)
+    fut.add_done_callback(
+        lambda future: loop.call_soon_threadsafe(
+            new_future._copy_state, future))
+    return new_future
diff --git a/trollius/locks.py b/trollius/locks.py
new file mode 100644
index 0000000..b2e516b
--- /dev/null
+++ b/trollius/locks.py
@@ -0,0 +1,470 @@
+"""Synchronization primitives."""
+
+__all__ = ['Lock', 'Event', 'Condition', 'Semaphore', 'BoundedSemaphore']
+
+import collections
+import sys
+
+from . import events
+from . import futures
+from .coroutines import coroutine
+
+
+_PY35 = sys.version_info >= (3, 5)
+
+
+class _ContextManager:
+    """Context manager.
+
+    This enables the following idiom for acquiring and releasing a
+    lock around a block:
+
+        with (yield from lock):
+            <block>
+
+    while failing loudly when accidentally using:
+
+        with lock:
+            <block>
+    """
+
+    def __init__(self, lock):
+        self._lock = lock
+
+    def __enter__(self):
+        # We have no use for the "as ..."  clause in the with
+        # statement for locks.
+        return None
+
+    def __exit__(self, *args):
+        try:
+            self._lock.release()
+        finally:
+            self._lock = None  # Crudely prevent reuse.
+
+
+class _ContextManagerMixin:
+    def __enter__(self):
+        raise RuntimeError(
+            '"yield from" should be used as context manager expression')
+
+    def __exit__(self, *args):
+        # This must exist because __enter__ exists, even though that
+        # always raises; that's how the with-statement works.
+        pass
+
+    @coroutine
+    def __iter__(self):
+        # This is not a coroutine.  It is meant to enable the idiom:
+        #
+        #     with (yield from lock):
+        #         <block>
+        #
+        # as an alternative to:
+        #
+        #     yield from lock.acquire()
+        #     try:
+        #         <block>
+        #     finally:
+        #         lock.release()
+        yield from self.acquire()
+        return _ContextManager(self)
+
+    if _PY35:
+
+        def __await__(self):
+            # To make "with await lock" work.
+            yield from self.acquire()
+            return _ContextManager(self)
+
+        @coroutine
+        def __aenter__(self):
+            yield from self.acquire()
+            # We have no use for the "as ..."  clause in the with
+            # statement for locks.
+            return None
+
+        @coroutine
+        def __aexit__(self, exc_type, exc, tb):
+            self.release()
+
+
+class Lock(_ContextManagerMixin):
+    """Primitive lock objects.
+
+    A primitive lock is a synchronization primitive that is not owned
+    by a particular coroutine when locked.  A primitive lock is in one
+    of two states, 'locked' or 'unlocked'.
+
+    It is created in the unlocked state.  It has two basic methods,
+    acquire() and release().  When the state is unlocked, acquire()
+    changes the state to locked and returns immediately.  When the
+    state is locked, acquire() blocks until a call to release() in
+    another coroutine changes it to unlocked, then the acquire() call
+    resets it to locked and returns.  The release() method should only
+    be called in the locked state; it changes the state to unlocked
+    and returns immediately.  If an attempt is made to release an
+    unlocked lock, a RuntimeError will be raised.
+
+    When more than one coroutine is blocked in acquire() waiting for
+    the state to turn to unlocked, only one coroutine proceeds when a
+    release() call resets the state to unlocked; first coroutine which
+    is blocked in acquire() is being processed.
+
+    acquire() is a coroutine and should be called with 'yield from'.
+
+    Locks also support the context management protocol.  '(yield from lock)'
+    should be used as context manager expression.
+
+    Usage:
+
+        lock = Lock()
+        ...
+        yield from lock
+        try:
+            ...
+        finally:
+            lock.release()
+
+    Context manager usage:
+
+        lock = Lock()
+        ...
+        with (yield from lock):
+             ...
+
+    Lock objects can be tested for locking state:
+
+        if not lock.locked():
+           yield from lock
+        else:
+           # lock is acquired
+           ...
+
+    """
+
+    def __init__(self, *, loop=None):
+        self._waiters = collections.deque()
+        self._locked = False
+        if loop is not None:
+            self._loop = loop
+        else:
+            self._loop = events.get_event_loop()
+
+    def __repr__(self):
+        res = super().__repr__()
+        extra = 'locked' if self._locked else 'unlocked'
+        if self._waiters:
+            extra = '{},waiters:{}'.format(extra, len(self._waiters))
+        return '<{} [{}]>'.format(res[1:-1], extra)
+
+    def locked(self):
+        """Return True if lock is acquired."""
+        return self._locked
+
+    @coroutine
+    def acquire(self):
+        """Acquire a lock.
+
+        This method blocks until the lock is unlocked, then sets it to
+        locked and returns True.
+        """
+        if not self._waiters and not self._locked:
+            self._locked = True
+            return True
+
+        fut = futures.Future(loop=self._loop)
+        self._waiters.append(fut)
+        try:
+            yield from fut
+            self._locked = True
+            return True
+        finally:
+            self._waiters.remove(fut)
+
+    def release(self):
+        """Release a lock.
+
+        When the lock is locked, reset it to unlocked, and return.
+        If any other coroutines are blocked waiting for the lock to become
+        unlocked, allow exactly one of them to proceed.
+
+        When invoked on an unlocked lock, a RuntimeError is raised.
+
+        There is no return value.
+        """
+        if self._locked:
+            self._locked = False
+            # Wake up the first waiter who isn't cancelled.
+            for fut in self._waiters:
+                if not fut.done():
+                    fut.set_result(True)
+                    break
+        else:
+            raise RuntimeError('Lock is not acquired.')
+
+
+class Event:
+    """Asynchronous equivalent to threading.Event.
+
+    Class implementing event objects. An event manages a flag that can be set
+    to true with the set() method and reset to false with the clear() method.
+    The wait() method blocks until the flag is true. The flag is initially
+    false.
+    """
+
+    def __init__(self, *, loop=None):
+        self._waiters = collections.deque()
+        self._value = False
+        if loop is not None:
+            self._loop = loop
+        else:
+            self._loop = events.get_event_loop()
+
+    def __repr__(self):
+        res = super().__repr__()
+        extra = 'set' if self._value else 'unset'
+        if self._waiters:
+            extra = '{},waiters:{}'.format(extra, len(self._waiters))
+        return '<{} [{}]>'.format(res[1:-1], extra)
+
+    def is_set(self):
+        """Return True if and only if the internal flag is true."""
+        return self._value
+
+    def set(self):
+        """Set the internal flag to true. All coroutines waiting for it to
+        become true are awakened. Coroutine that call wait() once the flag is
+        true will not block at all.
+        """
+        if not self._value:
+            self._value = True
+
+            for fut in self._waiters:
+                if not fut.done():
+                    fut.set_result(True)
+
+    def clear(self):
+        """Reset the internal flag to false. Subsequently, coroutines calling
+        wait() will block until set() is called to set the internal flag
+        to true again."""
+        self._value = False
+
+    @coroutine
+    def wait(self):
+        """Block until the internal flag is true.
+
+        If the internal flag is true on entry, return True
+        immediately.  Otherwise, block until another coroutine calls
+        set() to set the flag to true, then return True.
+        """
+        if self._value:
+            return True
+
+        fut = futures.Future(loop=self._loop)
+        self._waiters.append(fut)
+        try:
+            yield from fut
+            return True
+        finally:
+            self._waiters.remove(fut)
+
+
+class Condition(_ContextManagerMixin):
+    """Asynchronous equivalent to threading.Condition.
+
+    This class implements condition variable objects. A condition variable
+    allows one or more coroutines to wait until they are notified by another
+    coroutine.
+
+    A new Lock object is created and used as the underlying lock.
+    """
+
+    def __init__(self, lock=None, *, loop=None):
+        if loop is not None:
+            self._loop = loop
+        else:
+            self._loop = events.get_event_loop()
+
+        if lock is None:
+            lock = Lock(loop=self._loop)
+        elif lock._loop is not self._loop:
+            raise ValueError("loop argument must agree with lock")
+
+        self._lock = lock
+        # Export the lock's locked(), acquire() and release() methods.
+        self.locked = lock.locked
+        self.acquire = lock.acquire
+        self.release = lock.release
+
+        self._waiters = collections.deque()
+
+    def __repr__(self):
+        res = super().__repr__()
+        extra = 'locked' if self.locked() else 'unlocked'
+        if self._waiters:
+            extra = '{},waiters:{}'.format(extra, len(self._waiters))
+        return '<{} [{}]>'.format(res[1:-1], extra)
+
+    @coroutine
+    def wait(self):
+        """Wait until notified.
+
+        If the calling coroutine has not acquired the lock when this
+        method is called, a RuntimeError is raised.
+
+        This method releases the underlying lock, and then blocks
+        until it is awakened by a notify() or notify_all() call for
+        the same condition variable in another coroutine.  Once
+        awakened, it re-acquires the lock and returns True.
+        """
+        if not self.locked():
+            raise RuntimeError('cannot wait on un-acquired lock')
+
+        self.release()
+        try:
+            fut = futures.Future(loop=self._loop)
+            self._waiters.append(fut)
+            try:
+                yield from fut
+                return True
+            finally:
+                self._waiters.remove(fut)
+
+        finally:
+            yield from self.acquire()
+
+    @coroutine
+    def wait_for(self, predicate):
+        """Wait until a predicate becomes true.
+
+        The predicate should be a callable which result will be
+        interpreted as a boolean value.  The final predicate value is
+        the return value.
+        """
+        result = predicate()
+        while not result:
+            yield from self.wait()
+            result = predicate()
+        return result
+
+    def notify(self, n=1):
+        """By default, wake up one coroutine waiting on this condition, if any.
+        If the calling coroutine has not acquired the lock when this method
+        is called, a RuntimeError is raised.
+
+        This method wakes up at most n of the coroutines waiting for the
+        condition variable; it is a no-op if no coroutines are waiting.
+
+        Note: an awakened coroutine does not actually return from its
+        wait() call until it can reacquire the lock. Since notify() does
+        not release the lock, its caller should.
+        """
+        if not self.locked():
+            raise RuntimeError('cannot notify on un-acquired lock')
+
+        idx = 0
+        for fut in self._waiters:
+            if idx >= n:
+                break
+
+            if not fut.done():
+                idx += 1
+                fut.set_result(False)
+
+    def notify_all(self):
+        """Wake up all threads waiting on this condition. This method acts
+        like notify(), but wakes up all waiting threads instead of one. If the
+        calling thread has not acquired the lock when this method is called,
+        a RuntimeError is raised.
+        """
+        self.notify(len(self._waiters))
+
+
+class Semaphore(_ContextManagerMixin):
+    """A Semaphore implementation.
+
+    A semaphore manages an internal counter which is decremented by each
+    acquire() call and incremented by each release() call. The counter
+    can never go below zero; when acquire() finds that it is zero, it blocks,
+    waiting until some other thread calls release().
+
+    Semaphores also support the context management protocol.
+
+    The optional argument gives the initial value for the internal
+    counter; it defaults to 1. If the value given is less than 0,
+    ValueError is raised.
+    """
+
+    def __init__(self, value=1, *, loop=None):
+        if value < 0:
+            raise ValueError("Semaphore initial value must be >= 0")
+        self._value = value
+        self._waiters = collections.deque()
+        if loop is not None:
+            self._loop = loop
+        else:
+            self._loop = events.get_event_loop()
+
+    def __repr__(self):
+        res = super().__repr__()
+        extra = 'locked' if self.locked() else 'unlocked,value:{}'.format(
+            self._value)
+        if self._waiters:
+            extra = '{},waiters:{}'.format(extra, len(self._waiters))
+        return '<{} [{}]>'.format(res[1:-1], extra)
+
+    def locked(self):
+        """Returns True if semaphore can not be acquired immediately."""
+        return self._value == 0
+
+    @coroutine
+    def acquire(self):
+        """Acquire a semaphore.
+
+        If the internal counter is larger than zero on entry,
+        decrement it by one and return True immediately.  If it is
+        zero on entry, block, waiting until some other coroutine has
+        called release() to make it larger than 0, and then return
+        True.
+        """
+        if not self._waiters and self._value > 0:
+            self._value -= 1
+            return True
+
+        fut = futures.Future(loop=self._loop)
+        self._waiters.append(fut)
+        try:
+            yield from fut
+            self._value -= 1
+            return True
+        finally:
+            self._waiters.remove(fut)
+
+    def release(self):
+        """Release a semaphore, incrementing the internal counter by one.
+        When it was zero on entry and another coroutine is waiting for it to
+        become larger than zero again, wake up that coroutine.
+        """
+        self._value += 1
+        for waiter in self._waiters:
+            if not waiter.done():
+                waiter.set_result(True)
+                break
+
+
+class BoundedSemaphore(Semaphore):
+    """A bounded semaphore implementation.
+
+    This raises ValueError in release() if it would increase the value
+    above the initial value.
+    """
+
+    def __init__(self, value=1, *, loop=None):
+        self._bound_value = value
+        super().__init__(value, loop=loop)
+
+    def release(self):
+        if self._value >= self._bound_value:
+            raise ValueError('BoundedSemaphore released too many times')
+        super().release()
diff --git a/trollius/log.py b/trollius/log.py
new file mode 100644
index 0000000..23a7074
--- /dev/null
+++ b/trollius/log.py
@@ -0,0 +1,7 @@
+"""Logging configuration."""
+
+import logging
+
+
+# Name the logger after the package.
+logger = logging.getLogger(__package__)
diff --git a/trollius/proactor_events.py b/trollius/proactor_events.py
new file mode 100644
index 0000000..9c2b8f1
--- /dev/null
+++ b/trollius/proactor_events.py
@@ -0,0 +1,547 @@
+"""Event loop using a proactor and related classes.
+
+A proactor is a "notify-on-completion" multiplexer.  Currently a
+proactor is only implemented on Windows with IOCP.
+"""
+
+__all__ = ['BaseProactorEventLoop']
+
+import socket
+import sys
+import warnings
+
+from . import base_events
+from . import constants
+from . import futures
+from . import sslproto
+from . import transports
+from .log import logger
+
+
+class _ProactorBasePipeTransport(transports._FlowControlMixin,
+                                 transports.BaseTransport):
+    """Base class for pipe and socket transports."""
+
+    def __init__(self, loop, sock, protocol, waiter=None,
+                 extra=None, server=None):
+        super().__init__(extra, loop)
+        self._set_extra(sock)
+        self._sock = sock
+        self._protocol = protocol
+        self._server = server
+        self._buffer = None  # None or bytearray.
+        self._read_fut = None
+        self._write_fut = None
+        self._pending_write = 0
+        self._conn_lost = 0
+        self._closing = False  # Set when close() called.
+        self._eof_written = False
+        if self._server is not None:
+            self._server._attach()
+        self._loop.call_soon(self._protocol.connection_made, self)
+        if waiter is not None:
+            # only wake up the waiter when connection_made() has been called
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self._sock is None:
+            info.append('closed')
+        elif self._closing:
+            info.append('closing')
+        if self._sock is not None:
+            info.append('fd=%s' % self._sock.fileno())
+        if self._read_fut is not None:
+            info.append('read=%s' % self._read_fut)
+        if self._write_fut is not None:
+            info.append("write=%r" % self._write_fut)
+        if self._buffer:
+            bufsize = len(self._buffer)
+            info.append('write_bufsize=%s' % bufsize)
+        if self._eof_written:
+            info.append('EOF written')
+        return '<%s>' % ' '.join(info)
+
+    def _set_extra(self, sock):
+        self._extra['pipe'] = sock
+
+    def close(self):
+        if self._closing:
+            return
+        self._closing = True
+        self._conn_lost += 1
+        if not self._buffer and self._write_fut is None:
+            self._loop.call_soon(self._call_connection_lost, None)
+        if self._read_fut is not None:
+            self._read_fut.cancel()
+            self._read_fut = None
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if self._sock is not None:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self.close()
+
+    def _fatal_error(self, exc, message='Fatal error on pipe transport'):
+        if isinstance(exc, (BrokenPipeError, ConnectionResetError)):
+            if self._loop.get_debug():
+                logger.debug("%r: %s", self, message, exc_info=True)
+        else:
+            self._loop.call_exception_handler({
+                'message': message,
+                'exception': exc,
+                'transport': self,
+                'protocol': self._protocol,
+            })
+        self._force_close(exc)
+
+    def _force_close(self, exc):
+        if self._closing:
+            return
+        self._closing = True
+        self._conn_lost += 1
+        if self._write_fut:
+            self._write_fut.cancel()
+            self._write_fut = None
+        if self._read_fut:
+            self._read_fut.cancel()
+            self._read_fut = None
+        self._pending_write = 0
+        self._buffer = None
+        self._loop.call_soon(self._call_connection_lost, exc)
+
+    def _call_connection_lost(self, exc):
+        try:
+            self._protocol.connection_lost(exc)
+        finally:
+            # XXX If there is a pending overlapped read on the other
+            # end then it may fail with ERROR_NETNAME_DELETED if we
+            # just close our end.  First calling shutdown() seems to
+            # cure it, but maybe using DisconnectEx() would be better.
+            if hasattr(self._sock, 'shutdown'):
+                self._sock.shutdown(socket.SHUT_RDWR)
+            self._sock.close()
+            self._sock = None
+            server = self._server
+            if server is not None:
+                server._detach()
+                self._server = None
+
+    def get_write_buffer_size(self):
+        size = self._pending_write
+        if self._buffer is not None:
+            size += len(self._buffer)
+        return size
+
+
+class _ProactorReadPipeTransport(_ProactorBasePipeTransport,
+                                 transports.ReadTransport):
+    """Transport for read pipes."""
+
+    def __init__(self, loop, sock, protocol, waiter=None,
+                 extra=None, server=None):
+        super().__init__(loop, sock, protocol, waiter, extra, server)
+        self._paused = False
+        self._loop.call_soon(self._loop_reading)
+
+    def pause_reading(self):
+        if self._closing:
+            raise RuntimeError('Cannot pause_reading() when closing')
+        if self._paused:
+            raise RuntimeError('Already paused')
+        self._paused = True
+        if self._loop.get_debug():
+            logger.debug("%r pauses reading", self)
+
+    def resume_reading(self):
+        if not self._paused:
+            raise RuntimeError('Not paused')
+        self._paused = False
+        if self._closing:
+            return
+        self._loop.call_soon(self._loop_reading, self._read_fut)
+        if self._loop.get_debug():
+            logger.debug("%r resumes reading", self)
+
+    def _loop_reading(self, fut=None):
+        if self._paused:
+            return
+        data = None
+
+        try:
+            if fut is not None:
+                assert self._read_fut is fut or (self._read_fut is None and
+                                                 self._closing)
+                self._read_fut = None
+                data = fut.result()  # deliver data later in "finally" clause
+
+            if self._closing:
+                # since close() has been called we ignore any read data
+                data = None
+                return
+
+            if data == b'':
+                # we got end-of-file so no need to reschedule a new read
+                return
+
+            # reschedule a new read
+            self._read_fut = self._loop._proactor.recv(self._sock, 4096)
+        except ConnectionAbortedError as exc:
+            if not self._closing:
+                self._fatal_error(exc, 'Fatal read error on pipe transport')
+            elif self._loop.get_debug():
+                logger.debug("Read error on pipe transport while closing",
+                             exc_info=True)
+        except ConnectionResetError as exc:
+            self._force_close(exc)
+        except OSError as exc:
+            self._fatal_error(exc, 'Fatal read error on pipe transport')
+        except futures.CancelledError:
+            if not self._closing:
+                raise
+        else:
+            self._read_fut.add_done_callback(self._loop_reading)
+        finally:
+            if data:
+                self._protocol.data_received(data)
+            elif data is not None:
+                if self._loop.get_debug():
+                    logger.debug("%r received EOF", self)
+                keep_open = self._protocol.eof_received()
+                if not keep_open:
+                    self.close()
+
+
+class _ProactorBaseWritePipeTransport(_ProactorBasePipeTransport,
+                                      transports.WriteTransport):
+    """Transport for write pipes."""
+
+    def write(self, data):
+        if not isinstance(data, (bytes, bytearray, memoryview)):
+            raise TypeError('data argument must be byte-ish (%r)',
+                            type(data))
+        if self._eof_written:
+            raise RuntimeError('write_eof() already called')
+
+        if not data:
+            return
+
+        if self._conn_lost:
+            if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+                logger.warning('socket.send() raised exception.')
+            self._conn_lost += 1
+            return
+
+        # Observable states:
+        # 1. IDLE: _write_fut and _buffer both None
+        # 2. WRITING: _write_fut set; _buffer None
+        # 3. BACKED UP: _write_fut set; _buffer a bytearray
+        # We always copy the data, so the caller can't modify it
+        # while we're still waiting for the I/O to happen.
+        if self._write_fut is None:  # IDLE -> WRITING
+            assert self._buffer is None
+            # Pass a copy, except if it's already immutable.
+            self._loop_writing(data=bytes(data))
+        elif not self._buffer:  # WRITING -> BACKED UP
+            # Make a mutable copy which we can extend.
+            self._buffer = bytearray(data)
+            self._maybe_pause_protocol()
+        else:  # BACKED UP
+            # Append to buffer (also copies).
+            self._buffer.extend(data)
+            self._maybe_pause_protocol()
+
+    def _loop_writing(self, f=None, data=None):
+        try:
+            assert f is self._write_fut
+            self._write_fut = None
+            self._pending_write = 0
+            if f:
+                f.result()
+            if data is None:
+                data = self._buffer
+                self._buffer = None
+            if not data:
+                if self._closing:
+                    self._loop.call_soon(self._call_connection_lost, None)
+                if self._eof_written:
+                    self._sock.shutdown(socket.SHUT_WR)
+                # Now that we've reduced the buffer size, tell the
+                # protocol to resume writing if it was paused.  Note that
+                # we do this last since the callback is called immediately
+                # and it may add more data to the buffer (even causing the
+                # protocol to be paused again).
+                self._maybe_resume_protocol()
+            else:
+                self._write_fut = self._loop._proactor.send(self._sock, data)
+                if not self._write_fut.done():
+                    assert self._pending_write == 0
+                    self._pending_write = len(data)
+                    self._write_fut.add_done_callback(self._loop_writing)
+                    self._maybe_pause_protocol()
+                else:
+                    self._write_fut.add_done_callback(self._loop_writing)
+        except ConnectionResetError as exc:
+            self._force_close(exc)
+        except OSError as exc:
+            self._fatal_error(exc, 'Fatal write error on pipe transport')
+
+    def can_write_eof(self):
+        return True
+
+    def write_eof(self):
+        self.close()
+
+    def abort(self):
+        self._force_close(None)
+
+
+class _ProactorWritePipeTransport(_ProactorBaseWritePipeTransport):
+    def __init__(self, *args, **kw):
+        super().__init__(*args, **kw)
+        self._read_fut = self._loop._proactor.recv(self._sock, 16)
+        self._read_fut.add_done_callback(self._pipe_closed)
+
+    def _pipe_closed(self, fut):
+        if fut.cancelled():
+            # the transport has been closed
+            return
+        assert fut.result() == b''
+        if self._closing:
+            assert self._read_fut is None
+            return
+        assert fut is self._read_fut, (fut, self._read_fut)
+        self._read_fut = None
+        if self._write_fut is not None:
+            self._force_close(BrokenPipeError())
+        else:
+            self.close()
+
+
+class _ProactorDuplexPipeTransport(_ProactorReadPipeTransport,
+                                   _ProactorBaseWritePipeTransport,
+                                   transports.Transport):
+    """Transport for duplex pipes."""
+
+    def can_write_eof(self):
+        return False
+
+    def write_eof(self):
+        raise NotImplementedError
+
+
+class _ProactorSocketTransport(_ProactorReadPipeTransport,
+                               _ProactorBaseWritePipeTransport,
+                               transports.Transport):
+    """Transport for connected sockets."""
+
+    def _set_extra(self, sock):
+        self._extra['socket'] = sock
+        try:
+            self._extra['sockname'] = sock.getsockname()
+        except (socket.error, AttributeError):
+            if self._loop.get_debug():
+                logger.warning("getsockname() failed on %r",
+                             sock, exc_info=True)
+        if 'peername' not in self._extra:
+            try:
+                self._extra['peername'] = sock.getpeername()
+            except (socket.error, AttributeError):
+                if self._loop.get_debug():
+                    logger.warning("getpeername() failed on %r",
+                                   sock, exc_info=True)
+
+    def can_write_eof(self):
+        return True
+
+    def write_eof(self):
+        if self._closing or self._eof_written:
+            return
+        self._eof_written = True
+        if self._write_fut is None:
+            self._sock.shutdown(socket.SHUT_WR)
+
+
+class BaseProactorEventLoop(base_events.BaseEventLoop):
+
+    def __init__(self, proactor):
+        super().__init__()
+        logger.debug('Using proactor: %s', proactor.__class__.__name__)
+        self._proactor = proactor
+        self._selector = proactor   # convenient alias
+        self._self_reading_future = None
+        self._accept_futures = {}   # socket file descriptor => Future
+        proactor.set_loop(self)
+        self._make_self_pipe()
+
+    def _make_socket_transport(self, sock, protocol, waiter=None,
+                               extra=None, server=None):
+        return _ProactorSocketTransport(self, sock, protocol, waiter,
+                                        extra, server)
+
+    def _make_ssl_transport(self, rawsock, protocol, sslcontext, waiter=None,
+                            *, server_side=False, server_hostname=None,
+                            extra=None, server=None):
+        if not sslproto._is_sslproto_available():
+            raise NotImplementedError("Proactor event loop requires Python 3.5"
+                                      " or newer (ssl.MemoryBIO) to support "
+                                      "SSL")
+
+        ssl_protocol = sslproto.SSLProtocol(self, protocol, sslcontext, waiter,
+                                            server_side, server_hostname)
+        _ProactorSocketTransport(self, rawsock, ssl_protocol,
+                                 extra=extra, server=server)
+        return ssl_protocol._app_transport
+
+    def _make_duplex_pipe_transport(self, sock, protocol, waiter=None,
+                                    extra=None):
+        return _ProactorDuplexPipeTransport(self,
+                                            sock, protocol, waiter, extra)
+
+    def _make_read_pipe_transport(self, sock, protocol, waiter=None,
+                                  extra=None):
+        return _ProactorReadPipeTransport(self, sock, protocol, waiter, extra)
+
+    def _make_write_pipe_transport(self, sock, protocol, waiter=None,
+                                   extra=None):
+        # We want connection_lost() to be called when other end closes
+        return _ProactorWritePipeTransport(self,
+                                           sock, protocol, waiter, extra)
+
+    def close(self):
+        if self.is_running():
+            raise RuntimeError("Cannot close a running event loop")
+        if self.is_closed():
+            return
+
+        # Call these methods before closing the event loop (before calling
+        # BaseEventLoop.close), because they can schedule callbacks with
+        # call_soon(), which is forbidden when the event loop is closed.
+        self._stop_accept_futures()
+        self._close_self_pipe()
+        self._proactor.close()
+        self._proactor = None
+        self._selector = None
+
+        # Close the event loop
+        super().close()
+
+    def sock_recv(self, sock, n):
+        return self._proactor.recv(sock, n)
+
+    def sock_sendall(self, sock, data):
+        return self._proactor.send(sock, data)
+
+    def sock_connect(self, sock, address):
+        try:
+            if self._debug:
+                base_events._check_resolved_address(sock, address)
+        except ValueError as err:
+            fut = futures.Future(loop=self)
+            fut.set_exception(err)
+            return fut
+        else:
+            return self._proactor.connect(sock, address)
+
+    def sock_accept(self, sock):
+        return self._proactor.accept(sock)
+
+    def _socketpair(self):
+        raise NotImplementedError
+
+    def _close_self_pipe(self):
+        if self._self_reading_future is not None:
+            self._self_reading_future.cancel()
+            self._self_reading_future = None
+        self._ssock.close()
+        self._ssock = None
+        self._csock.close()
+        self._csock = None
+        self._internal_fds -= 1
+
+    def _make_self_pipe(self):
+        # A self-socket, really. :-)
+        self._ssock, self._csock = self._socketpair()
+        self._ssock.setblocking(False)
+        self._csock.setblocking(False)
+        self._internal_fds += 1
+        self.call_soon(self._loop_self_reading)
+
+    def _loop_self_reading(self, f=None):
+        try:
+            if f is not None:
+                f.result()  # may raise
+            f = self._proactor.recv(self._ssock, 4096)
+        except futures.CancelledError:
+            # _close_self_pipe() has been called, stop waiting for data
+            return
+        except Exception as exc:
+            self.call_exception_handler({
+                'message': 'Error on reading from the event loop self pipe',
+                'exception': exc,
+                'loop': self,
+            })
+        else:
+            self._self_reading_future = f
+            f.add_done_callback(self._loop_self_reading)
+
+    def _write_to_self(self):
+        self._csock.send(b'\0')
+
+    def _start_serving(self, protocol_factory, sock,
+                       sslcontext=None, server=None):
+
+        def loop(f=None):
+            try:
+                if f is not None:
+                    conn, addr = f.result()
+                    if self._debug:
+                        logger.debug("%r got a new connection from %r: %r",
+                                     server, addr, conn)
+                    protocol = protocol_factory()
+                    if sslcontext is not None:
+                        self._make_ssl_transport(
+                            conn, protocol, sslcontext, server_side=True,
+                            extra={'peername': addr}, server=server)
+                    else:
+                        self._make_socket_transport(
+                            conn, protocol,
+                            extra={'peername': addr}, server=server)
+                if self.is_closed():
+                    return
+                f = self._proactor.accept(sock)
+            except OSError as exc:
+                if sock.fileno() != -1:
+                    self.call_exception_handler({
+                        'message': 'Accept failed on a socket',
+                        'exception': exc,
+                        'socket': sock,
+                    })
+                    sock.close()
+                elif self._debug:
+                    logger.debug("Accept failed on socket %r",
+                                 sock, exc_info=True)
+            except futures.CancelledError:
+                sock.close()
+            else:
+                self._accept_futures[sock.fileno()] = f
+                f.add_done_callback(loop)
+
+        self.call_soon(loop)
+
+    def _process_events(self, event_list):
+        # Events are processed in the IocpProactor._poll() method
+        pass
+
+    def _stop_accept_futures(self):
+        for future in self._accept_futures.values():
+            future.cancel()
+        self._accept_futures.clear()
+
+    def _stop_serving(self, sock):
+        self._stop_accept_futures()
+        self._proactor._stop_serving(sock)
+        sock.close()
diff --git a/trollius/protocols.py b/trollius/protocols.py
new file mode 100644
index 0000000..80fcac9
--- /dev/null
+++ b/trollius/protocols.py
@@ -0,0 +1,134 @@
+"""Abstract Protocol class."""
+
+__all__ = ['BaseProtocol', 'Protocol', 'DatagramProtocol',
+           'SubprocessProtocol']
+
+
+class BaseProtocol:
+    """Common base class for protocol interfaces.
+
+    Usually user implements protocols that derived from BaseProtocol
+    like Protocol or ProcessProtocol.
+
+    The only case when BaseProtocol should be implemented directly is
+    write-only transport like write pipe
+    """
+
+    def connection_made(self, transport):
+        """Called when a connection is made.
+
+        The argument is the transport representing the pipe connection.
+        To receive data, wait for data_received() calls.
+        When the connection is closed, connection_lost() is called.
+        """
+
+    def connection_lost(self, exc):
+        """Called when the connection is lost or closed.
+
+        The argument is an exception object or None (the latter
+        meaning a regular EOF is received or the connection was
+        aborted or closed).
+        """
+
+    def pause_writing(self):
+        """Called when the transport's buffer goes over the high-water mark.
+
+        Pause and resume calls are paired -- pause_writing() is called
+        once when the buffer goes strictly over the high-water mark
+        (even if subsequent writes increases the buffer size even
+        more), and eventually resume_writing() is called once when the
+        buffer size reaches the low-water mark.
+
+        Note that if the buffer size equals the high-water mark,
+        pause_writing() is not called -- it must go strictly over.
+        Conversely, resume_writing() is called when the buffer size is
+        equal or lower than the low-water mark.  These end conditions
+        are important to ensure that things go as expected when either
+        mark is zero.
+
+        NOTE: This is the only Protocol callback that is not called
+        through EventLoop.call_soon() -- if it were, it would have no
+        effect when it's most needed (when the app keeps writing
+        without yielding until pause_writing() is called).
+        """
+
+    def resume_writing(self):
+        """Called when the transport's buffer drains below the low-water mark.
+
+        See pause_writing() for details.
+        """
+
+
+class Protocol(BaseProtocol):
+    """Interface for stream protocol.
+
+    The user should implement this interface.  They can inherit from
+    this class but don't need to.  The implementations here do
+    nothing (they don't raise exceptions).
+
+    When the user wants to requests a transport, they pass a protocol
+    factory to a utility function (e.g., EventLoop.create_connection()).
+
+    When the connection is made successfully, connection_made() is
+    called with a suitable transport object.  Then data_received()
+    will be called 0 or more times with data (bytes) received from the
+    transport; finally, connection_lost() will be called exactly once
+    with either an exception object or None as an argument.
+
+    State machine of calls:
+
+      start -> CM [-> DR*] [-> ER?] -> CL -> end
+
+    * CM: connection_made()
+    * DR: data_received()
+    * ER: eof_received()
+    * CL: connection_lost()
+    """
+
+    def data_received(self, data):
+        """Called when some data is received.
+
+        The argument is a bytes object.
+        """
+
+    def eof_received(self):
+        """Called when the other end calls write_eof() or equivalent.
+
+        If this returns a false value (including None), the transport
+        will close itself.  If it returns a true value, closing the
+        transport is up to the protocol.
+        """
+
+
+class DatagramProtocol(BaseProtocol):
+    """Interface for datagram protocol."""
+
+    def datagram_received(self, data, addr):
+        """Called when some datagram is received."""
+
+    def error_received(self, exc):
+        """Called when a send or receive operation raises an OSError.
+
+        (Other than BlockingIOError or InterruptedError.)
+        """
+
+
+class SubprocessProtocol(BaseProtocol):
+    """Interface for protocol for subprocess calls."""
+
+    def pipe_data_received(self, fd, data):
+        """Called when the subprocess writes data into stdout/stderr pipe.
+
+        fd is int file descriptor.
+        data is bytes object.
+        """
+
+    def pipe_connection_lost(self, fd, exc):
+        """Called when a file descriptor associated with the child process is
+        closed.
+
+        fd is the int file descriptor that was closed.
+        """
+
+    def process_exited(self):
+        """Called when subprocess has exited."""
diff --git a/trollius/queues.py b/trollius/queues.py
new file mode 100644
index 0000000..ed11662
--- /dev/null
+++ b/trollius/queues.py
@@ -0,0 +1,293 @@
+"""Queues"""
+
+__all__ = ['Queue', 'PriorityQueue', 'LifoQueue', 'QueueFull', 'QueueEmpty',
+           'JoinableQueue']
+
+import collections
+import heapq
+
+from . import events
+from . import futures
+from . import locks
+from .tasks import coroutine
+
+
+class QueueEmpty(Exception):
+    """Exception raised when Queue.get_nowait() is called on a Queue object
+    which is empty.
+    """
+    pass
+
+
+class QueueFull(Exception):
+    """Exception raised when the Queue.put_nowait() method is called on a Queue
+    object which is full.
+    """
+    pass
+
+
+class Queue:
+    """A queue, useful for coordinating producer and consumer coroutines.
+
+    If maxsize is less than or equal to zero, the queue size is infinite. If it
+    is an integer greater than 0, then "yield from put()" will block when the
+    queue reaches maxsize, until an item is removed by get().
+
+    Unlike the standard library Queue, you can reliably know this Queue's size
+    with qsize(), since your single-threaded asyncio application won't be
+    interrupted between calling qsize() and doing an operation on the Queue.
+    """
+
+    def __init__(self, maxsize=0, *, loop=None):
+        if loop is None:
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
+        self._maxsize = maxsize
+
+        # Futures.
+        self._getters = collections.deque()
+        # Pairs of (item, Future).
+        self._putters = collections.deque()
+        self._unfinished_tasks = 0
+        self._finished = locks.Event(loop=self._loop)
+        self._finished.set()
+        self._init(maxsize)
+
+    # These three are overridable in subclasses.
+
+    def _init(self, maxsize):
+        self._queue = collections.deque()
+
+    def _get(self):
+        return self._queue.popleft()
+
+    def _put(self, item):
+        self._queue.append(item)
+
+    # End of the overridable methods.
+
+    def __put_internal(self, item):
+        self._put(item)
+        self._unfinished_tasks += 1
+        self._finished.clear()
+
+    def __repr__(self):
+        return '<{} at {:#x} {}>'.format(
+            type(self).__name__, id(self), self._format())
+
+    def __str__(self):
+        return '<{} {}>'.format(type(self).__name__, self._format())
+
+    def _format(self):
+        result = 'maxsize={!r}'.format(self._maxsize)
+        if getattr(self, '_queue', None):
+            result += ' _queue={!r}'.format(list(self._queue))
+        if self._getters:
+            result += ' _getters[{}]'.format(len(self._getters))
+        if self._putters:
+            result += ' _putters[{}]'.format(len(self._putters))
+        if self._unfinished_tasks:
+            result += ' tasks={}'.format(self._unfinished_tasks)
+        return result
+
+    def _consume_done_getters(self):
+        # Delete waiters at the head of the get() queue who've timed out.
+        while self._getters and self._getters[0].done():
+            self._getters.popleft()
+
+    def _consume_done_putters(self):
+        # Delete waiters at the head of the put() queue who've timed out.
+        while self._putters and self._putters[0][1].done():
+            self._putters.popleft()
+
+    def qsize(self):
+        """Number of items in the queue."""
+        return len(self._queue)
+
+    @property
+    def maxsize(self):
+        """Number of items allowed in the queue."""
+        return self._maxsize
+
+    def empty(self):
+        """Return True if the queue is empty, False otherwise."""
+        return not self._queue
+
+    def full(self):
+        """Return True if there are maxsize items in the queue.
+
+        Note: if the Queue was initialized with maxsize=0 (the default),
+        then full() is never True.
+        """
+        if self._maxsize <= 0:
+            return False
+        else:
+            return self.qsize() >= self._maxsize
+
+    @coroutine
+    def put(self, item):
+        """Put an item into the queue.
+
+        Put an item into the queue. If the queue is full, wait until a free
+        slot is available before adding item.
+
+        This method is a coroutine.
+        """
+        self._consume_done_getters()
+        if self._getters:
+            assert not self._queue, (
+                'queue non-empty, why are getters waiting?')
+
+            getter = self._getters.popleft()
+            self.__put_internal(item)
+
+            # getter cannot be cancelled, we just removed done getters
+            getter.set_result(self._get())
+
+        elif self._maxsize > 0 and self._maxsize <= self.qsize():
+            waiter = futures.Future(loop=self._loop)
+
+            self._putters.append((item, waiter))
+            yield from waiter
+
+        else:
+            self.__put_internal(item)
+
+    def put_nowait(self, item):
+        """Put an item into the queue without blocking.
+
+        If no free slot is immediately available, raise QueueFull.
+        """
+        self._consume_done_getters()
+        if self._getters:
+            assert not self._queue, (
+                'queue non-empty, why are getters waiting?')
+
+            getter = self._getters.popleft()
+            self.__put_internal(item)
+
+            # getter cannot be cancelled, we just removed done getters
+            getter.set_result(self._get())
+
+        elif self._maxsize > 0 and self._maxsize <= self.qsize():
+            raise QueueFull
+        else:
+            self.__put_internal(item)
+
+    @coroutine
+    def get(self):
+        """Remove and return an item from the queue.
+
+        If queue is empty, wait until an item is available.
+
+        This method is a coroutine.
+        """
+        self._consume_done_putters()
+        if self._putters:
+            assert self.full(), 'queue not full, why are putters waiting?'
+            item, putter = self._putters.popleft()
+            self.__put_internal(item)
+
+            # When a getter runs and frees up a slot so this putter can
+            # run, we need to defer the put for a tick to ensure that
+            # getters and putters alternate perfectly. See
+            # ChannelTest.test_wait.
+            self._loop.call_soon(putter._set_result_unless_cancelled, None)
+
+            return self._get()
+
+        elif self.qsize():
+            return self._get()
+        else:
+            waiter = futures.Future(loop=self._loop)
+
+            self._getters.append(waiter)
+            return (yield from waiter)
+
+    def get_nowait(self):
+        """Remove and return an item from the queue.
+
+        Return an item if one is immediately available, else raise QueueEmpty.
+        """
+        self._consume_done_putters()
+        if self._putters:
+            assert self.full(), 'queue not full, why are putters waiting?'
+            item, putter = self._putters.popleft()
+            self.__put_internal(item)
+            # Wake putter on next tick.
+
+            # getter cannot be cancelled, we just removed done putters
+            putter.set_result(None)
+
+            return self._get()
+
+        elif self.qsize():
+            return self._get()
+        else:
+            raise QueueEmpty
+
+    def task_done(self):
+        """Indicate that a formerly enqueued task is complete.
+
+        Used by queue consumers. For each get() used to fetch a task,
+        a subsequent call to task_done() tells the queue that the processing
+        on the task is complete.
+
+        If a join() is currently blocking, it will resume when all items have
+        been processed (meaning that a task_done() call was received for every
+        item that had been put() into the queue).
+
+        Raises ValueError if called more times than there were items placed in
+        the queue.
+        """
+        if self._unfinished_tasks <= 0:
+            raise ValueError('task_done() called too many times')
+        self._unfinished_tasks -= 1
+        if self._unfinished_tasks == 0:
+            self._finished.set()
+
+    @coroutine
+    def join(self):
+        """Block until all items in the queue have been gotten and processed.
+
+        The count of unfinished tasks goes up whenever an item is added to the
+        queue. The count goes down whenever a consumer calls task_done() to
+        indicate that the item was retrieved and all work on it is complete.
+        When the count of unfinished tasks drops to zero, join() unblocks.
+        """
+        if self._unfinished_tasks > 0:
+            yield from self._finished.wait()
+
+
+class PriorityQueue(Queue):
+    """A subclass of Queue; retrieves entries in priority order (lowest first).
+
+    Entries are typically tuples of the form: (priority number, data).
+    """
+
+    def _init(self, maxsize):
+        self._queue = []
+
+    def _put(self, item, heappush=heapq.heappush):
+        heappush(self._queue, item)
+
+    def _get(self, heappop=heapq.heappop):
+        return heappop(self._queue)
+
+
+class LifoQueue(Queue):
+    """A subclass of Queue that retrieves most recently added entries first."""
+
+    def _init(self, maxsize):
+        self._queue = []
+
+    def _put(self, item):
+        self._queue.append(item)
+
+    def _get(self):
+        return self._queue.pop()
+
+
+JoinableQueue = Queue
+"""Deprecated alias for Queue."""
diff --git a/trollius/selector_events.py b/trollius/selector_events.py
new file mode 100644
index 0000000..7c5b9b5
--- /dev/null
+++ b/trollius/selector_events.py
@@ -0,0 +1,1068 @@
+"""Event loop using a selector and related classes.
+
+A selector is a "notify-when-ready" multiplexer.  For a subclass which
+also includes support for signal handling, see the unix_events sub-module.
+"""
+
+__all__ = ['BaseSelectorEventLoop']
+
+import collections
+import errno
+import functools
+import socket
+import sys
+import warnings
+try:
+    import ssl
+except ImportError:  # pragma: no cover
+    ssl = None
+
+from . import base_events
+from . import constants
+from . import events
+from . import futures
+from . import selectors
+from . import transports
+from . import sslproto
+from .coroutines import coroutine
+from .log import logger
+
+
+def _test_selector_event(selector, fd, event):
+    # Test if the selector is monitoring 'event' events
+    # for the file descriptor 'fd'.
+    try:
+        key = selector.get_key(fd)
+    except KeyError:
+        return False
+    else:
+        return bool(key.events & event)
+
+
+class BaseSelectorEventLoop(base_events.BaseEventLoop):
+    """Selector event loop.
+
+    See events.EventLoop for API specification.
+    """
+
+    def __init__(self, selector=None):
+        super().__init__()
+
+        if selector is None:
+            selector = selectors.DefaultSelector()
+        logger.debug('Using selector: %s', selector.__class__.__name__)
+        self._selector = selector
+        self._make_self_pipe()
+
+    def _make_socket_transport(self, sock, protocol, waiter=None, *,
+                               extra=None, server=None):
+        return _SelectorSocketTransport(self, sock, protocol, waiter,
+                                        extra, server)
+
+    def _make_ssl_transport(self, rawsock, protocol, sslcontext, waiter=None,
+                            *, server_side=False, server_hostname=None,
+                            extra=None, server=None):
+        if not sslproto._is_sslproto_available():
+            return self._make_legacy_ssl_transport(
+                rawsock, protocol, sslcontext, waiter,
+                server_side=server_side, server_hostname=server_hostname,
+                extra=extra, server=server)
+
+        ssl_protocol = sslproto.SSLProtocol(self, protocol, sslcontext, waiter,
+                                            server_side, server_hostname)
+        _SelectorSocketTransport(self, rawsock, ssl_protocol,
+                                 extra=extra, server=server)
+        return ssl_protocol._app_transport
+
+    def _make_legacy_ssl_transport(self, rawsock, protocol, sslcontext,
+                                   waiter, *,
+                                   server_side=False, server_hostname=None,
+                                   extra=None, server=None):
+        # Use the legacy API: SSL_write, SSL_read, etc. The legacy API is used
+        # on Python 3.4 and older, when ssl.MemoryBIO is not available.
+        return _SelectorSslTransport(
+            self, rawsock, protocol, sslcontext, waiter,
+            server_side, server_hostname, extra, server)
+
+    def _make_datagram_transport(self, sock, protocol,
+                                 address=None, waiter=None, extra=None):
+        return _SelectorDatagramTransport(self, sock, protocol,
+                                          address, waiter, extra)
+
+    def close(self):
+        if self.is_running():
+            raise RuntimeError("Cannot close a running event loop")
+        if self.is_closed():
+            return
+        self._close_self_pipe()
+        super().close()
+        if self._selector is not None:
+            self._selector.close()
+            self._selector = None
+
+    def _socketpair(self):
+        raise NotImplementedError
+
+    def _close_self_pipe(self):
+        self.remove_reader(self._ssock.fileno())
+        self._ssock.close()
+        self._ssock = None
+        self._csock.close()
+        self._csock = None
+        self._internal_fds -= 1
+
+    def _make_self_pipe(self):
+        # A self-socket, really. :-)
+        self._ssock, self._csock = self._socketpair()
+        self._ssock.setblocking(False)
+        self._csock.setblocking(False)
+        self._internal_fds += 1
+        self.add_reader(self._ssock.fileno(), self._read_from_self)
+
+    def _process_self_data(self, data):
+        pass
+
+    def _read_from_self(self):
+        while True:
+            try:
+                data = self._ssock.recv(4096)
+                if not data:
+                    break
+                self._process_self_data(data)
+            except InterruptedError:
+                continue
+            except BlockingIOError:
+                break
+
+    def _write_to_self(self):
+        # This may be called from a different thread, possibly after
+        # _close_self_pipe() has been called or even while it is
+        # running.  Guard for self._csock being None or closed.  When
+        # a socket is closed, send() raises OSError (with errno set to
+        # EBADF, but let's not rely on the exact error code).
+        csock = self._csock
+        if csock is not None:
+            try:
+                csock.send(b'\0')
+            except OSError:
+                if self._debug:
+                    logger.debug("Fail to write a null byte into the "
+                                 "self-pipe socket",
+                                 exc_info=True)
+
+    def _start_serving(self, protocol_factory, sock,
+                       sslcontext=None, server=None):
+        self.add_reader(sock.fileno(), self._accept_connection,
+                        protocol_factory, sock, sslcontext, server)
+
+    def _accept_connection(self, protocol_factory, sock,
+                           sslcontext=None, server=None):
+        try:
+            conn, addr = sock.accept()
+            if self._debug:
+                logger.debug("%r got a new connection from %r: %r",
+                             server, addr, conn)
+            conn.setblocking(False)
+        except (BlockingIOError, InterruptedError, ConnectionAbortedError):
+            pass  # False alarm.
+        except OSError as exc:
+            # There's nowhere to send the error, so just log it.
+            if exc.errno in (errno.EMFILE, errno.ENFILE,
+                             errno.ENOBUFS, errno.ENOMEM):
+                # Some platforms (e.g. Linux keep reporting the FD as
+                # ready, so we remove the read handler temporarily.
+                # We'll try again in a while.
+                self.call_exception_handler({
+                    'message': 'socket.accept() out of system resource',
+                    'exception': exc,
+                    'socket': sock,
+                })
+                self.remove_reader(sock.fileno())
+                self.call_later(constants.ACCEPT_RETRY_DELAY,
+                                self._start_serving,
+                                protocol_factory, sock, sslcontext, server)
+            else:
+                raise  # The event loop will catch, log and ignore it.
+        else:
+            extra = {'peername': addr}
+            accept = self._accept_connection2(protocol_factory, conn, extra,
+                                              sslcontext, server)
+            self.create_task(accept)
+
+    @coroutine
+    def _accept_connection2(self, protocol_factory, conn, extra,
+                            sslcontext=None, server=None):
+        protocol = None
+        transport = None
+        try:
+            protocol = protocol_factory()
+            waiter = futures.Future(loop=self)
+            if sslcontext:
+                transport = self._make_ssl_transport(
+                    conn, protocol, sslcontext, waiter=waiter,
+                    server_side=True, extra=extra, server=server)
+            else:
+                transport = self._make_socket_transport(
+                    conn, protocol, waiter=waiter, extra=extra,
+                    server=server)
+
+            try:
+                yield from waiter
+            except:
+                transport.close()
+                raise
+
+            # It's now up to the protocol to handle the connection.
+        except Exception as exc:
+            if self._debug:
+                context = {
+                    'message': ('Error on transport creation '
+                                'for incoming connection'),
+                    'exception': exc,
+                }
+                if protocol is not None:
+                    context['protocol'] = protocol
+                if transport is not None:
+                    context['transport'] = transport
+                self.call_exception_handler(context)
+
+    def add_reader(self, fd, callback, *args):
+        """Add a reader callback."""
+        self._check_closed()
+        handle = events.Handle(callback, args, self)
+        try:
+            key = self._selector.get_key(fd)
+        except KeyError:
+            self._selector.register(fd, selectors.EVENT_READ,
+                                    (handle, None))
+        else:
+            mask, (reader, writer) = key.events, key.data
+            self._selector.modify(fd, mask | selectors.EVENT_READ,
+                                  (handle, writer))
+            if reader is not None:
+                reader.cancel()
+
+    def remove_reader(self, fd):
+        """Remove a reader callback."""
+        if self.is_closed():
+            return False
+        try:
+            key = self._selector.get_key(fd)
+        except KeyError:
+            return False
+        else:
+            mask, (reader, writer) = key.events, key.data
+            mask &= ~selectors.EVENT_READ
+            if not mask:
+                self._selector.unregister(fd)
+            else:
+                self._selector.modify(fd, mask, (None, writer))
+
+            if reader is not None:
+                reader.cancel()
+                return True
+            else:
+                return False
+
+    def add_writer(self, fd, callback, *args):
+        """Add a writer callback.."""
+        self._check_closed()
+        handle = events.Handle(callback, args, self)
+        try:
+            key = self._selector.get_key(fd)
+        except KeyError:
+            self._selector.register(fd, selectors.EVENT_WRITE,
+                                    (None, handle))
+        else:
+            mask, (reader, writer) = key.events, key.data
+            self._selector.modify(fd, mask | selectors.EVENT_WRITE,
+                                  (reader, handle))
+            if writer is not None:
+                writer.cancel()
+
+    def remove_writer(self, fd):
+        """Remove a writer callback."""
+        if self.is_closed():
+            return False
+        try:
+            key = self._selector.get_key(fd)
+        except KeyError:
+            return False
+        else:
+            mask, (reader, writer) = key.events, key.data
+            # Remove both writer and connector.
+            mask &= ~selectors.EVENT_WRITE
+            if not mask:
+                self._selector.unregister(fd)
+            else:
+                self._selector.modify(fd, mask, (reader, None))
+
+            if writer is not None:
+                writer.cancel()
+                return True
+            else:
+                return False
+
+    def sock_recv(self, sock, n):
+        """Receive data from the socket.
+
+        The return value is a bytes object representing the data received.
+        The maximum amount of data to be received at once is specified by
+        nbytes.
+
+        This method is a coroutine.
+        """
+        if self._debug and sock.gettimeout() != 0:
+            raise ValueError("the socket must be non-blocking")
+        fut = futures.Future(loop=self)
+        self._sock_recv(fut, False, sock, n)
+        return fut
+
+    def _sock_recv(self, fut, registered, sock, n):
+        # _sock_recv() can add itself as an I/O callback if the operation can't
+        # be done immediately. Don't use it directly, call sock_recv().
+        fd = sock.fileno()
+        if registered:
+            # Remove the callback early.  It should be rare that the
+            # selector says the fd is ready but the call still returns
+            # EAGAIN, and I am willing to take a hit in that case in
+            # order to simplify the common case.
+            self.remove_reader(fd)
+        if fut.cancelled():
+            return
+        try:
+            data = sock.recv(n)
+        except (BlockingIOError, InterruptedError):
+            self.add_reader(fd, self._sock_recv, fut, True, sock, n)
+        except Exception as exc:
+            fut.set_exception(exc)
+        else:
+            fut.set_result(data)
+
+    def sock_sendall(self, sock, data):
+        """Send data to the socket.
+
+        The socket must be connected to a remote socket. This method continues
+        to send data from data until either all data has been sent or an
+        error occurs. None is returned on success. On error, an exception is
+        raised, and there is no way to determine how much data, if any, was
+        successfully processed by the receiving end of the connection.
+
+        This method is a coroutine.
+        """
+        if self._debug and sock.gettimeout() != 0:
+            raise ValueError("the socket must be non-blocking")
+        fut = futures.Future(loop=self)
+        if data:
+            self._sock_sendall(fut, False, sock, data)
+        else:
+            fut.set_result(None)
+        return fut
+
+    def _sock_sendall(self, fut, registered, sock, data):
+        fd = sock.fileno()
+
+        if registered:
+            self.remove_writer(fd)
+        if fut.cancelled():
+            return
+
+        try:
+            n = sock.send(data)
+        except (BlockingIOError, InterruptedError):
+            n = 0
+        except Exception as exc:
+            fut.set_exception(exc)
+            return
+
+        if n == len(data):
+            fut.set_result(None)
+        else:
+            if n:
+                data = data[n:]
+            self.add_writer(fd, self._sock_sendall, fut, True, sock, data)
+
+    def sock_connect(self, sock, address):
+        """Connect to a remote socket at address.
+
+        The address must be already resolved to avoid the trap of hanging the
+        entire event loop when the address requires doing a DNS lookup. For
+        example, it must be an IP address, not an hostname, for AF_INET and
+        AF_INET6 address families. Use getaddrinfo() to resolve the hostname
+        asynchronously.
+
+        This method is a coroutine.
+        """
+        if self._debug and sock.gettimeout() != 0:
+            raise ValueError("the socket must be non-blocking")
+        fut = futures.Future(loop=self)
+        try:
+            if self._debug:
+                base_events._check_resolved_address(sock, address)
+        except ValueError as err:
+            fut.set_exception(err)
+        else:
+            self._sock_connect(fut, sock, address)
+        return fut
+
+    def _sock_connect(self, fut, sock, address):
+        fd = sock.fileno()
+        try:
+            sock.connect(address)
+        except (BlockingIOError, InterruptedError):
+            # Issue #23618: When the C function connect() fails with EINTR, the
+            # connection runs in background. We have to wait until the socket
+            # becomes writable to be notified when the connection succeed or
+            # fails.
+            fut.add_done_callback(functools.partial(self._sock_connect_done,
+                                                    fd))
+            self.add_writer(fd, self._sock_connect_cb, fut, sock, address)
+        except Exception as exc:
+            fut.set_exception(exc)
+        else:
+            fut.set_result(None)
+
+    def _sock_connect_done(self, fd, fut):
+        self.remove_writer(fd)
+
+    def _sock_connect_cb(self, fut, sock, address):
+        if fut.cancelled():
+            return
+
+        try:
+            err = sock.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR)
+            if err != 0:
+                # Jump to any except clause below.
+                raise OSError(err, 'Connect call failed %s' % (address,))
+        except (BlockingIOError, InterruptedError):
+            # socket is still registered, the callback will be retried later
+            pass
+        except Exception as exc:
+            fut.set_exception(exc)
+        else:
+            fut.set_result(None)
+
+    def sock_accept(self, sock):
+        """Accept a connection.
+
+        The socket must be bound to an address and listening for connections.
+        The return value is a pair (conn, address) where conn is a new socket
+        object usable to send and receive data on the connection, and address
+        is the address bound to the socket on the other end of the connection.
+
+        This method is a coroutine.
+        """
+        if self._debug and sock.gettimeout() != 0:
+            raise ValueError("the socket must be non-blocking")
+        fut = futures.Future(loop=self)
+        self._sock_accept(fut, False, sock)
+        return fut
+
+    def _sock_accept(self, fut, registered, sock):
+        fd = sock.fileno()
+        if registered:
+            self.remove_reader(fd)
+        if fut.cancelled():
+            return
+        try:
+            conn, address = sock.accept()
+            conn.setblocking(False)
+        except (BlockingIOError, InterruptedError):
+            self.add_reader(fd, self._sock_accept, fut, True, sock)
+        except Exception as exc:
+            fut.set_exception(exc)
+        else:
+            fut.set_result((conn, address))
+
+    def _process_events(self, event_list):
+        for key, mask in event_list:
+            fileobj, (reader, writer) = key.fileobj, key.data
+            if mask & selectors.EVENT_READ and reader is not None:
+                if reader._cancelled:
+                    self.remove_reader(fileobj)
+                else:
+                    self._add_callback(reader)
+            if mask & selectors.EVENT_WRITE and writer is not None:
+                if writer._cancelled:
+                    self.remove_writer(fileobj)
+                else:
+                    self._add_callback(writer)
+
+    def _stop_serving(self, sock):
+        self.remove_reader(sock.fileno())
+        sock.close()
+
+
+class _SelectorTransport(transports._FlowControlMixin,
+                         transports.Transport):
+
+    max_size = 256 * 1024  # Buffer size passed to recv().
+
+    _buffer_factory = bytearray  # Constructs initial value for self._buffer.
+
+    # Attribute used in the destructor: it must be set even if the constructor
+    # is not called (see _SelectorSslTransport which may start by raising an
+    # exception)
+    _sock = None
+
+    def __init__(self, loop, sock, protocol, extra=None, server=None):
+        super().__init__(extra, loop)
+        self._extra['socket'] = sock
+        self._extra['sockname'] = sock.getsockname()
+        if 'peername' not in self._extra:
+            try:
+                self._extra['peername'] = sock.getpeername()
+            except socket.error:
+                self._extra['peername'] = None
+        self._sock = sock
+        self._sock_fd = sock.fileno()
+        self._protocol = protocol
+        self._protocol_connected = True
+        self._server = server
+        self._buffer = self._buffer_factory()
+        self._conn_lost = 0  # Set when call to connection_lost scheduled.
+        self._closing = False  # Set when close() called.
+        if self._server is not None:
+            self._server._attach()
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self._sock is None:
+            info.append('closed')
+        elif self._closing:
+            info.append('closing')
+        info.append('fd=%s' % self._sock_fd)
+        # test if the transport was closed
+        if self._loop is not None and not self._loop.is_closed():
+            polling = _test_selector_event(self._loop._selector,
+                                           self._sock_fd, selectors.EVENT_READ)
+            if polling:
+                info.append('read=polling')
+            else:
+                info.append('read=idle')
+
+            polling = _test_selector_event(self._loop._selector,
+                                           self._sock_fd,
+                                           selectors.EVENT_WRITE)
+            if polling:
+                state = 'polling'
+            else:
+                state = 'idle'
+
+            bufsize = self.get_write_buffer_size()
+            info.append('write=<%s, bufsize=%s>' % (state, bufsize))
+        return '<%s>' % ' '.join(info)
+
+    def abort(self):
+        self._force_close(None)
+
+    def close(self):
+        if self._closing:
+            return
+        self._closing = True
+        self._loop.remove_reader(self._sock_fd)
+        if not self._buffer:
+            self._conn_lost += 1
+            self._loop.call_soon(self._call_connection_lost, None)
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if self._sock is not None:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self._sock.close()
+
+    def _fatal_error(self, exc, message='Fatal error on transport'):
+        # Should be called from exception handler only.
+        if isinstance(exc, (BrokenPipeError,
+                            ConnectionResetError, ConnectionAbortedError)):
+            if self._loop.get_debug():
+                logger.debug("%r: %s", self, message, exc_info=True)
+        else:
+            self._loop.call_exception_handler({
+                'message': message,
+                'exception': exc,
+                'transport': self,
+                'protocol': self._protocol,
+            })
+        self._force_close(exc)
+
+    def _force_close(self, exc):
+        if self._conn_lost:
+            return
+        if self._buffer:
+            self._buffer.clear()
+            self._loop.remove_writer(self._sock_fd)
+        if not self._closing:
+            self._closing = True
+            self._loop.remove_reader(self._sock_fd)
+        self._conn_lost += 1
+        self._loop.call_soon(self._call_connection_lost, exc)
+
+    def _call_connection_lost(self, exc):
+        try:
+            if self._protocol_connected:
+                self._protocol.connection_lost(exc)
+        finally:
+            self._sock.close()
+            self._sock = None
+            self._protocol = None
+            self._loop = None
+            server = self._server
+            if server is not None:
+                server._detach()
+                self._server = None
+
+    def get_write_buffer_size(self):
+        return len(self._buffer)
+
+
+class _SelectorSocketTransport(_SelectorTransport):
+
+    def __init__(self, loop, sock, protocol, waiter=None,
+                 extra=None, server=None):
+        super().__init__(loop, sock, protocol, extra, server)
+        self._eof = False
+        self._paused = False
+
+        self._loop.call_soon(self._protocol.connection_made, self)
+        # only start reading when connection_made() has been called
+        self._loop.call_soon(self._loop.add_reader,
+                             self._sock_fd, self._read_ready)
+        if waiter is not None:
+            # only wake up the waiter when connection_made() has been called
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
+
+    def pause_reading(self):
+        if self._closing:
+            raise RuntimeError('Cannot pause_reading() when closing')
+        if self._paused:
+            raise RuntimeError('Already paused')
+        self._paused = True
+        self._loop.remove_reader(self._sock_fd)
+        if self._loop.get_debug():
+            logger.debug("%r pauses reading", self)
+
+    def resume_reading(self):
+        if not self._paused:
+            raise RuntimeError('Not paused')
+        self._paused = False
+        if self._closing:
+            return
+        self._loop.add_reader(self._sock_fd, self._read_ready)
+        if self._loop.get_debug():
+            logger.debug("%r resumes reading", self)
+
+    def _read_ready(self):
+        try:
+            data = self._sock.recv(self.max_size)
+        except (BlockingIOError, InterruptedError):
+            pass
+        except Exception as exc:
+            self._fatal_error(exc, 'Fatal read error on socket transport')
+        else:
+            if data:
+                self._protocol.data_received(data)
+            else:
+                if self._loop.get_debug():
+                    logger.debug("%r received EOF", self)
+                keep_open = self._protocol.eof_received()
+                if keep_open:
+                    # We're keeping the connection open so the
+                    # protocol can write more, but we still can't
+                    # receive more, so remove the reader callback.
+                    self._loop.remove_reader(self._sock_fd)
+                else:
+                    self.close()
+
+    def write(self, data):
+        if not isinstance(data, (bytes, bytearray, memoryview)):
+            raise TypeError('data argument must be byte-ish (%r)',
+                            type(data))
+        if self._eof:
+            raise RuntimeError('Cannot call write() after write_eof()')
+        if not data:
+            return
+
+        if self._conn_lost:
+            if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+                logger.warning('socket.send() raised exception.')
+            self._conn_lost += 1
+            return
+
+        if not self._buffer:
+            # Optimization: try to send now.
+            try:
+                n = self._sock.send(data)
+            except (BlockingIOError, InterruptedError):
+                pass
+            except Exception as exc:
+                self._fatal_error(exc, 'Fatal write error on socket transport')
+                return
+            else:
+                data = data[n:]
+                if not data:
+                    return
+            # Not all was written; register write handler.
+            self._loop.add_writer(self._sock_fd, self._write_ready)
+
+        # Add it to the buffer.
+        self._buffer.extend(data)
+        self._maybe_pause_protocol()
+
+    def _write_ready(self):
+        assert self._buffer, 'Data should not be empty'
+
+        try:
+            n = self._sock.send(self._buffer)
+        except (BlockingIOError, InterruptedError):
+            pass
+        except Exception as exc:
+            self._loop.remove_writer(self._sock_fd)
+            self._buffer.clear()
+            self._fatal_error(exc, 'Fatal write error on socket transport')
+        else:
+            if n:
+                del self._buffer[:n]
+            self._maybe_resume_protocol()  # May append to buffer.
+            if not self._buffer:
+                self._loop.remove_writer(self._sock_fd)
+                if self._closing:
+                    self._call_connection_lost(None)
+                elif self._eof:
+                    self._sock.shutdown(socket.SHUT_WR)
+
+    def write_eof(self):
+        if self._eof:
+            return
+        self._eof = True
+        if not self._buffer:
+            self._sock.shutdown(socket.SHUT_WR)
+
+    def can_write_eof(self):
+        return True
+
+
+class _SelectorSslTransport(_SelectorTransport):
+
+    _buffer_factory = bytearray
+
+    def __init__(self, loop, rawsock, protocol, sslcontext, waiter=None,
+                 server_side=False, server_hostname=None,
+                 extra=None, server=None):
+        if ssl is None:
+            raise RuntimeError('stdlib ssl module not available')
+
+        if not sslcontext:
+            sslcontext = sslproto._create_transport_context(server_side, server_hostname)
+
+        wrap_kwargs = {
+            'server_side': server_side,
+            'do_handshake_on_connect': False,
+        }
+        if server_hostname and not server_side:
+            wrap_kwargs['server_hostname'] = server_hostname
+        sslsock = sslcontext.wrap_socket(rawsock, **wrap_kwargs)
+
+        super().__init__(loop, sslsock, protocol, extra, server)
+        # the protocol connection is only made after the SSL handshake
+        self._protocol_connected = False
+
+        self._server_hostname = server_hostname
+        self._waiter = waiter
+        self._sslcontext = sslcontext
+        self._paused = False
+
+        # SSL-specific extra info.  (peercert is set later)
+        self._extra.update(sslcontext=sslcontext)
+
+        if self._loop.get_debug():
+            logger.debug("%r starts SSL handshake", self)
+            start_time = self._loop.time()
+        else:
+            start_time = None
+        self._on_handshake(start_time)
+
+    def _wakeup_waiter(self, exc=None):
+        if self._waiter is None:
+            return
+        if not self._waiter.cancelled():
+            if exc is not None:
+                self._waiter.set_exception(exc)
+            else:
+                self._waiter.set_result(None)
+        self._waiter = None
+
+    def _on_handshake(self, start_time):
+        try:
+            self._sock.do_handshake()
+        except ssl.SSLWantReadError:
+            self._loop.add_reader(self._sock_fd,
+                                  self._on_handshake, start_time)
+            return
+        except ssl.SSLWantWriteError:
+            self._loop.add_writer(self._sock_fd,
+                                  self._on_handshake, start_time)
+            return
+        except BaseException as exc:
+            if self._loop.get_debug():
+                logger.warning("%r: SSL handshake failed",
+                               self, exc_info=True)
+            self._loop.remove_reader(self._sock_fd)
+            self._loop.remove_writer(self._sock_fd)
+            self._sock.close()
+            self._wakeup_waiter(exc)
+            if isinstance(exc, Exception):
+                return
+            else:
+                raise
+
+        self._loop.remove_reader(self._sock_fd)
+        self._loop.remove_writer(self._sock_fd)
+
+        peercert = self._sock.getpeercert()
+        if not hasattr(self._sslcontext, 'check_hostname'):
+            # Verify hostname if requested, Python 3.4+ uses check_hostname
+            # and checks the hostname in do_handshake()
+            if (self._server_hostname and
+                self._sslcontext.verify_mode != ssl.CERT_NONE):
+                try:
+                    ssl.match_hostname(peercert, self._server_hostname)
+                except Exception as exc:
+                    if self._loop.get_debug():
+                        logger.warning("%r: SSL handshake failed "
+                                       "on matching the hostname",
+                                       self, exc_info=True)
+                    self._sock.close()
+                    self._wakeup_waiter(exc)
+                    return
+
+        # Add extra info that becomes available after handshake.
+        self._extra.update(peercert=peercert,
+                           cipher=self._sock.cipher(),
+                           compression=self._sock.compression(),
+                           )
+
+        self._read_wants_write = False
+        self._write_wants_read = False
+        self._loop.add_reader(self._sock_fd, self._read_ready)
+        self._protocol_connected = True
+        self._loop.call_soon(self._protocol.connection_made, self)
+        # only wake up the waiter when connection_made() has been called
+        self._loop.call_soon(self._wakeup_waiter)
+
+        if self._loop.get_debug():
+            dt = self._loop.time() - start_time
+            logger.debug("%r: SSL handshake took %.1f ms", self, dt * 1e3)
+
+    def pause_reading(self):
+        # XXX This is a bit icky, given the comment at the top of
+        # _read_ready().  Is it possible to evoke a deadlock?  I don't
+        # know, although it doesn't look like it; write() will still
+        # accept more data for the buffer and eventually the app will
+        # call resume_reading() again, and things will flow again.
+
+        if self._closing:
+            raise RuntimeError('Cannot pause_reading() when closing')
+        if self._paused:
+            raise RuntimeError('Already paused')
+        self._paused = True
+        self._loop.remove_reader(self._sock_fd)
+        if self._loop.get_debug():
+            logger.debug("%r pauses reading", self)
+
+    def resume_reading(self):
+        if not self._paused:
+            raise RuntimeError('Not paused')
+        self._paused = False
+        if self._closing:
+            return
+        self._loop.add_reader(self._sock_fd, self._read_ready)
+        if self._loop.get_debug():
+            logger.debug("%r resumes reading", self)
+
+    def _read_ready(self):
+        if self._write_wants_read:
+            self._write_wants_read = False
+            self._write_ready()
+
+            if self._buffer:
+                self._loop.add_writer(self._sock_fd, self._write_ready)
+
+        try:
+            data = self._sock.recv(self.max_size)
+        except (BlockingIOError, InterruptedError, ssl.SSLWantReadError):
+            pass
+        except ssl.SSLWantWriteError:
+            self._read_wants_write = True
+            self._loop.remove_reader(self._sock_fd)
+            self._loop.add_writer(self._sock_fd, self._write_ready)
+        except Exception as exc:
+            self._fatal_error(exc, 'Fatal read error on SSL transport')
+        else:
+            if data:
+                self._protocol.data_received(data)
+            else:
+                try:
+                    if self._loop.get_debug():
+                        logger.debug("%r received EOF", self)
+                    keep_open = self._protocol.eof_received()
+                    if keep_open:
+                        logger.warning('returning true from eof_received() '
+                                       'has no effect when using ssl')
+                finally:
+                    self.close()
+
+    def _write_ready(self):
+        if self._read_wants_write:
+            self._read_wants_write = False
+            self._read_ready()
+
+            if not (self._paused or self._closing):
+                self._loop.add_reader(self._sock_fd, self._read_ready)
+
+        if self._buffer:
+            try:
+                n = self._sock.send(self._buffer)
+            except (BlockingIOError, InterruptedError, ssl.SSLWantWriteError):
+                n = 0
+            except ssl.SSLWantReadError:
+                n = 0
+                self._loop.remove_writer(self._sock_fd)
+                self._write_wants_read = True
+            except Exception as exc:
+                self._loop.remove_writer(self._sock_fd)
+                self._buffer.clear()
+                self._fatal_error(exc, 'Fatal write error on SSL transport')
+                return
+
+            if n:
+                del self._buffer[:n]
+
+        self._maybe_resume_protocol()  # May append to buffer.
+
+        if not self._buffer:
+            self._loop.remove_writer(self._sock_fd)
+            if self._closing:
+                self._call_connection_lost(None)
+
+    def write(self, data):
+        if not isinstance(data, (bytes, bytearray, memoryview)):
+            raise TypeError('data argument must be byte-ish (%r)',
+                            type(data))
+        if not data:
+            return
+
+        if self._conn_lost:
+            if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+                logger.warning('socket.send() raised exception.')
+            self._conn_lost += 1
+            return
+
+        if not self._buffer:
+            self._loop.add_writer(self._sock_fd, self._write_ready)
+
+        # Add it to the buffer.
+        self._buffer.extend(data)
+        self._maybe_pause_protocol()
+
+    def can_write_eof(self):
+        return False
+
+
+class _SelectorDatagramTransport(_SelectorTransport):
+
+    _buffer_factory = collections.deque
+
+    def __init__(self, loop, sock, protocol, address=None,
+                 waiter=None, extra=None):
+        super().__init__(loop, sock, protocol, extra)
+        self._address = address
+        self._loop.call_soon(self._protocol.connection_made, self)
+        # only start reading when connection_made() has been called
+        self._loop.call_soon(self._loop.add_reader,
+                             self._sock_fd, self._read_ready)
+        if waiter is not None:
+            # only wake up the waiter when connection_made() has been called
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
+
+    def get_write_buffer_size(self):
+        return sum(len(data) for data, _ in self._buffer)
+
+    def _read_ready(self):
+        try:
+            data, addr = self._sock.recvfrom(self.max_size)
+        except (BlockingIOError, InterruptedError):
+            pass
+        except OSError as exc:
+            self._protocol.error_received(exc)
+        except Exception as exc:
+            self._fatal_error(exc, 'Fatal read error on datagram transport')
+        else:
+            self._protocol.datagram_received(data, addr)
+
+    def sendto(self, data, addr=None):
+        if not isinstance(data, (bytes, bytearray, memoryview)):
+            raise TypeError('data argument must be byte-ish (%r)',
+                            type(data))
+        if not data:
+            return
+
+        if self._address and addr not in (None, self._address):
+            raise ValueError('Invalid address: must be None or %s' %
+                             (self._address,))
+
+        if self._conn_lost and self._address:
+            if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+                logger.warning('socket.send() raised exception.')
+            self._conn_lost += 1
+            return
+
+        if not self._buffer:
+            # Attempt to send it right away first.
+            try:
+                if self._address:
+                    self._sock.send(data)
+                else:
+                    self._sock.sendto(data, addr)
+                return
+            except (BlockingIOError, InterruptedError):
+                self._loop.add_writer(self._sock_fd, self._sendto_ready)
+            except OSError as exc:
+                self._protocol.error_received(exc)
+                return
+            except Exception as exc:
+                self._fatal_error(exc,
+                                  'Fatal write error on datagram transport')
+                return
+
+        # Ensure that what we buffer is immutable.
+        self._buffer.append((bytes(data), addr))
+        self._maybe_pause_protocol()
+
+    def _sendto_ready(self):
+        while self._buffer:
+            data, addr = self._buffer.popleft()
+            try:
+                if self._address:
+                    self._sock.send(data)
+                else:
+                    self._sock.sendto(data, addr)
+            except (BlockingIOError, InterruptedError):
+                self._buffer.appendleft((data, addr))  # Try again later.
+                break
+            except OSError as exc:
+                self._protocol.error_received(exc)
+                return
+            except Exception as exc:
+                self._fatal_error(exc,
+                                  'Fatal write error on datagram transport')
+                return
+
+        self._maybe_resume_protocol()  # May append to buffer.
+        if not self._buffer:
+            self._loop.remove_writer(self._sock_fd)
+            if self._closing:
+                self._call_connection_lost(None)
diff --git a/trollius/selectors.py b/trollius/selectors.py
new file mode 100644
index 0000000..6d569c3
--- /dev/null
+++ b/trollius/selectors.py
@@ -0,0 +1,594 @@
+"""Selectors module.
+
+This module allows high-level and efficient I/O multiplexing, built upon the
+`select` module primitives.
+"""
+
+
+from abc import ABCMeta, abstractmethod
+from collections import namedtuple, Mapping
+import math
+import select
+import sys
+
+
+# generic events, that must be mapped to implementation-specific ones
+EVENT_READ = (1 << 0)
+EVENT_WRITE = (1 << 1)
+
+
+def _fileobj_to_fd(fileobj):
+    """Return a file descriptor from a file object.
+
+    Parameters:
+    fileobj -- file object or file descriptor
+
+    Returns:
+    corresponding file descriptor
+
+    Raises:
+    ValueError if the object is invalid
+    """
+    if isinstance(fileobj, int):
+        fd = fileobj
+    else:
+        try:
+            fd = int(fileobj.fileno())
+        except (AttributeError, TypeError, ValueError):
+            raise ValueError("Invalid file object: "
+                             "{!r}".format(fileobj)) from None
+    if fd < 0:
+        raise ValueError("Invalid file descriptor: {}".format(fd))
+    return fd
+
+
+SelectorKey = namedtuple('SelectorKey', ['fileobj', 'fd', 'events', 'data'])
+"""Object used to associate a file object to its backing file descriptor,
+selected event mask and attached data."""
+
+
+class _SelectorMapping(Mapping):
+    """Mapping of file objects to selector keys."""
+
+    def __init__(self, selector):
+        self._selector = selector
+
+    def __len__(self):
+        return len(self._selector._fd_to_key)
+
+    def __getitem__(self, fileobj):
+        try:
+            fd = self._selector._fileobj_lookup(fileobj)
+            return self._selector._fd_to_key[fd]
+        except KeyError:
+            raise KeyError("{!r} is not registered".format(fileobj)) from None
+
+    def __iter__(self):
+        return iter(self._selector._fd_to_key)
+
+
+class BaseSelector(metaclass=ABCMeta):
+    """Selector abstract base class.
+
+    A selector supports registering file objects to be monitored for specific
+    I/O events.
+
+    A file object is a file descriptor or any object with a `fileno()` method.
+    An arbitrary object can be attached to the file object, which can be used
+    for example to store context information, a callback, etc.
+
+    A selector can use various implementations (select(), poll(), epoll()...)
+    depending on the platform. The default `Selector` class uses the most
+    efficient implementation on the current platform.
+    """
+
+    @abstractmethod
+    def register(self, fileobj, events, data=None):
+        """Register a file object.
+
+        Parameters:
+        fileobj -- file object or file descriptor
+        events  -- events to monitor (bitwise mask of EVENT_READ|EVENT_WRITE)
+        data    -- attached data
+
+        Returns:
+        SelectorKey instance
+
+        Raises:
+        ValueError if events is invalid
+        KeyError if fileobj is already registered
+        OSError if fileobj is closed or otherwise is unacceptable to
+                the underlying system call (if a system call is made)
+
+        Note:
+        OSError may or may not be raised
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def unregister(self, fileobj):
+        """Unregister a file object.
+
+        Parameters:
+        fileobj -- file object or file descriptor
+
+        Returns:
+        SelectorKey instance
+
+        Raises:
+        KeyError if fileobj is not registered
+
+        Note:
+        If fileobj is registered but has since been closed this does
+        *not* raise OSError (even if the wrapped syscall does)
+        """
+        raise NotImplementedError
+
+    def modify(self, fileobj, events, data=None):
+        """Change a registered file object monitored events or attached data.
+
+        Parameters:
+        fileobj -- file object or file descriptor
+        events  -- events to monitor (bitwise mask of EVENT_READ|EVENT_WRITE)
+        data    -- attached data
+
+        Returns:
+        SelectorKey instance
+
+        Raises:
+        Anything that unregister() or register() raises
+        """
+        self.unregister(fileobj)
+        return self.register(fileobj, events, data)
+
+    @abstractmethod
+    def select(self, timeout=None):
+        """Perform the actual selection, until some monitored file objects are
+        ready or a timeout expires.
+
+        Parameters:
+        timeout -- if timeout > 0, this specifies the maximum wait time, in
+                   seconds
+                   if timeout <= 0, the select() call won't block, and will
+                   report the currently ready file objects
+                   if timeout is None, select() will block until a monitored
+                   file object becomes ready
+
+        Returns:
+        list of (key, events) for ready file objects
+        `events` is a bitwise mask of EVENT_READ|EVENT_WRITE
+        """
+        raise NotImplementedError
+
+    def close(self):
+        """Close the selector.
+
+        This must be called to make sure that any underlying resource is freed.
+        """
+        pass
+
+    def get_key(self, fileobj):
+        """Return the key associated to a registered file object.
+
+        Returns:
+        SelectorKey for this file object
+        """
+        mapping = self.get_map()
+        if mapping is None:
+            raise RuntimeError('Selector is closed')
+        try:
+            return mapping[fileobj]
+        except KeyError:
+            raise KeyError("{!r} is not registered".format(fileobj)) from None
+
+    @abstractmethod
+    def get_map(self):
+        """Return a mapping of file objects to selector keys."""
+        raise NotImplementedError
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *args):
+        self.close()
+
+
+class _BaseSelectorImpl(BaseSelector):
+    """Base selector implementation."""
+
+    def __init__(self):
+        # this maps file descriptors to keys
+        self._fd_to_key = {}
+        # read-only mapping returned by get_map()
+        self._map = _SelectorMapping(self)
+
+    def _fileobj_lookup(self, fileobj):
+        """Return a file descriptor from a file object.
+
+        This wraps _fileobj_to_fd() to do an exhaustive search in case
+        the object is invalid but we still have it in our map.  This
+        is used by unregister() so we can unregister an object that
+        was previously registered even if it is closed.  It is also
+        used by _SelectorMapping.
+        """
+        try:
+            return _fileobj_to_fd(fileobj)
+        except ValueError:
+            # Do an exhaustive search.
+            for key in self._fd_to_key.values():
+                if key.fileobj is fileobj:
+                    return key.fd
+            # Raise ValueError after all.
+            raise
+
+    def register(self, fileobj, events, data=None):
+        if (not events) or (events & ~(EVENT_READ | EVENT_WRITE)):
+            raise ValueError("Invalid events: {!r}".format(events))
+
+        key = SelectorKey(fileobj, self._fileobj_lookup(fileobj), events, data)
+
+        if key.fd in self._fd_to_key:
+            raise KeyError("{!r} (FD {}) is already registered"
+                           .format(fileobj, key.fd))
+
+        self._fd_to_key[key.fd] = key
+        return key
+
+    def unregister(self, fileobj):
+        try:
+            key = self._fd_to_key.pop(self._fileobj_lookup(fileobj))
+        except KeyError:
+            raise KeyError("{!r} is not registered".format(fileobj)) from None
+        return key
+
+    def modify(self, fileobj, events, data=None):
+        # TODO: Subclasses can probably optimize this even further.
+        try:
+            key = self._fd_to_key[self._fileobj_lookup(fileobj)]
+        except KeyError:
+            raise KeyError("{!r} is not registered".format(fileobj)) from None
+        if events != key.events:
+            self.unregister(fileobj)
+            key = self.register(fileobj, events, data)
+        elif data != key.data:
+            # Use a shortcut to update the data.
+            key = key._replace(data=data)
+            self._fd_to_key[key.fd] = key
+        return key
+
+    def close(self):
+        self._fd_to_key.clear()
+        self._map = None
+
+    def get_map(self):
+        return self._map
+
+    def _key_from_fd(self, fd):
+        """Return the key associated to a given file descriptor.
+
+        Parameters:
+        fd -- file descriptor
+
+        Returns:
+        corresponding key, or None if not found
+        """
+        try:
+            return self._fd_to_key[fd]
+        except KeyError:
+            return None
+
+
+class SelectSelector(_BaseSelectorImpl):
+    """Select-based selector."""
+
+    def __init__(self):
+        super().__init__()
+        self._readers = set()
+        self._writers = set()
+
+    def register(self, fileobj, events, data=None):
+        key = super().register(fileobj, events, data)
+        if events & EVENT_READ:
+            self._readers.add(key.fd)
+        if events & EVENT_WRITE:
+            self._writers.add(key.fd)
+        return key
+
+    def unregister(self, fileobj):
+        key = super().unregister(fileobj)
+        self._readers.discard(key.fd)
+        self._writers.discard(key.fd)
+        return key
+
+    if sys.platform == 'win32':
+        def _select(self, r, w, _, timeout=None):
+            r, w, x = select.select(r, w, w, timeout)
+            return r, w + x, []
+    else:
+        _select = select.select
+
+    def select(self, timeout=None):
+        timeout = None if timeout is None else max(timeout, 0)
+        ready = []
+        try:
+            r, w, _ = self._select(self._readers, self._writers, [], timeout)
+        except InterruptedError:
+            return ready
+        r = set(r)
+        w = set(w)
+        for fd in r | w:
+            events = 0
+            if fd in r:
+                events |= EVENT_READ
+            if fd in w:
+                events |= EVENT_WRITE
+
+            key = self._key_from_fd(fd)
+            if key:
+                ready.append((key, events & key.events))
+        return ready
+
+
+if hasattr(select, 'poll'):
+
+    class PollSelector(_BaseSelectorImpl):
+        """Poll-based selector."""
+
+        def __init__(self):
+            super().__init__()
+            self._poll = select.poll()
+
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            poll_events = 0
+            if events & EVENT_READ:
+                poll_events |= select.POLLIN
+            if events & EVENT_WRITE:
+                poll_events |= select.POLLOUT
+            self._poll.register(key.fd, poll_events)
+            return key
+
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            self._poll.unregister(key.fd)
+            return key
+
+        def select(self, timeout=None):
+            if timeout is None:
+                timeout = None
+            elif timeout <= 0:
+                timeout = 0
+            else:
+                # poll() has a resolution of 1 millisecond, round away from
+                # zero to wait *at least* timeout seconds.
+                timeout = math.ceil(timeout * 1e3)
+            ready = []
+            try:
+                fd_event_list = self._poll.poll(timeout)
+            except InterruptedError:
+                return ready
+            for fd, event in fd_event_list:
+                events = 0
+                if event & ~select.POLLIN:
+                    events |= EVENT_WRITE
+                if event & ~select.POLLOUT:
+                    events |= EVENT_READ
+
+                key = self._key_from_fd(fd)
+                if key:
+                    ready.append((key, events & key.events))
+            return ready
+
+
+if hasattr(select, 'epoll'):
+
+    class EpollSelector(_BaseSelectorImpl):
+        """Epoll-based selector."""
+
+        def __init__(self):
+            super().__init__()
+            self._epoll = select.epoll()
+
+        def fileno(self):
+            return self._epoll.fileno()
+
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            epoll_events = 0
+            if events & EVENT_READ:
+                epoll_events |= select.EPOLLIN
+            if events & EVENT_WRITE:
+                epoll_events |= select.EPOLLOUT
+            self._epoll.register(key.fd, epoll_events)
+            return key
+
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            try:
+                self._epoll.unregister(key.fd)
+            except OSError:
+                # This can happen if the FD was closed since it
+                # was registered.
+                pass
+            return key
+
+        def select(self, timeout=None):
+            if timeout is None:
+                timeout = -1
+            elif timeout <= 0:
+                timeout = 0
+            else:
+                # epoll_wait() has a resolution of 1 millisecond, round away
+                # from zero to wait *at least* timeout seconds.
+                timeout = math.ceil(timeout * 1e3) * 1e-3
+
+            # epoll_wait() expects `maxevents` to be greater than zero;
+            # we want to make sure that `select()` can be called when no
+            # FD is registered.
+            max_ev = max(len(self._fd_to_key), 1)
+
+            ready = []
+            try:
+                fd_event_list = self._epoll.poll(timeout, max_ev)
+            except InterruptedError:
+                return ready
+            for fd, event in fd_event_list:
+                events = 0
+                if event & ~select.EPOLLIN:
+                    events |= EVENT_WRITE
+                if event & ~select.EPOLLOUT:
+                    events |= EVENT_READ
+
+                key = self._key_from_fd(fd)
+                if key:
+                    ready.append((key, events & key.events))
+            return ready
+
+        def close(self):
+            self._epoll.close()
+            super().close()
+
+
+if hasattr(select, 'devpoll'):
+
+    class DevpollSelector(_BaseSelectorImpl):
+        """Solaris /dev/poll selector."""
+
+        def __init__(self):
+            super().__init__()
+            self._devpoll = select.devpoll()
+
+        def fileno(self):
+            return self._devpoll.fileno()
+
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            poll_events = 0
+            if events & EVENT_READ:
+                poll_events |= select.POLLIN
+            if events & EVENT_WRITE:
+                poll_events |= select.POLLOUT
+            self._devpoll.register(key.fd, poll_events)
+            return key
+
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            self._devpoll.unregister(key.fd)
+            return key
+
+        def select(self, timeout=None):
+            if timeout is None:
+                timeout = None
+            elif timeout <= 0:
+                timeout = 0
+            else:
+                # devpoll() has a resolution of 1 millisecond, round away from
+                # zero to wait *at least* timeout seconds.
+                timeout = math.ceil(timeout * 1e3)
+            ready = []
+            try:
+                fd_event_list = self._devpoll.poll(timeout)
+            except InterruptedError:
+                return ready
+            for fd, event in fd_event_list:
+                events = 0
+                if event & ~select.POLLIN:
+                    events |= EVENT_WRITE
+                if event & ~select.POLLOUT:
+                    events |= EVENT_READ
+
+                key = self._key_from_fd(fd)
+                if key:
+                    ready.append((key, events & key.events))
+            return ready
+
+        def close(self):
+            self._devpoll.close()
+            super().close()
+
+
+if hasattr(select, 'kqueue'):
+
+    class KqueueSelector(_BaseSelectorImpl):
+        """Kqueue-based selector."""
+
+        def __init__(self):
+            super().__init__()
+            self._kqueue = select.kqueue()
+
+        def fileno(self):
+            return self._kqueue.fileno()
+
+        def register(self, fileobj, events, data=None):
+            key = super().register(fileobj, events, data)
+            if events & EVENT_READ:
+                kev = select.kevent(key.fd, select.KQ_FILTER_READ,
+                                    select.KQ_EV_ADD)
+                self._kqueue.control([kev], 0, 0)
+            if events & EVENT_WRITE:
+                kev = select.kevent(key.fd, select.KQ_FILTER_WRITE,
+                                    select.KQ_EV_ADD)
+                self._kqueue.control([kev], 0, 0)
+            return key
+
+        def unregister(self, fileobj):
+            key = super().unregister(fileobj)
+            if key.events & EVENT_READ:
+                kev = select.kevent(key.fd, select.KQ_FILTER_READ,
+                                    select.KQ_EV_DELETE)
+                try:
+                    self._kqueue.control([kev], 0, 0)
+                except OSError:
+                    # This can happen if the FD was closed since it
+                    # was registered.
+                    pass
+            if key.events & EVENT_WRITE:
+                kev = select.kevent(key.fd, select.KQ_FILTER_WRITE,
+                                    select.KQ_EV_DELETE)
+                try:
+                    self._kqueue.control([kev], 0, 0)
+                except OSError:
+                    # See comment above.
+                    pass
+            return key
+
+        def select(self, timeout=None):
+            timeout = None if timeout is None else max(timeout, 0)
+            max_ev = len(self._fd_to_key)
+            ready = []
+            try:
+                kev_list = self._kqueue.control(None, max_ev, timeout)
+            except InterruptedError:
+                return ready
+            for kev in kev_list:
+                fd = kev.ident
+                flag = kev.filter
+                events = 0
+                if flag == select.KQ_FILTER_READ:
+                    events |= EVENT_READ
+                if flag == select.KQ_FILTER_WRITE:
+                    events |= EVENT_WRITE
+
+                key = self._key_from_fd(fd)
+                if key:
+                    ready.append((key, events & key.events))
+            return ready
+
+        def close(self):
+            self._kqueue.close()
+            super().close()
+
+
+# Choose the best implementation, roughly:
+#    epoll|kqueue|devpoll > poll > select.
+# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
+if 'KqueueSelector' in globals():
+    DefaultSelector = KqueueSelector
+elif 'EpollSelector' in globals():
+    DefaultSelector = EpollSelector
+elif 'DevpollSelector' in globals():
+    DefaultSelector = DevpollSelector
+elif 'PollSelector' in globals():
+    DefaultSelector = PollSelector
+else:
+    DefaultSelector = SelectSelector
diff --git a/trollius/sslproto.py b/trollius/sslproto.py
new file mode 100644
index 0000000..235855e
--- /dev/null
+++ b/trollius/sslproto.py
@@ -0,0 +1,668 @@
+import collections
+import sys
+import warnings
+try:
+    import ssl
+except ImportError:  # pragma: no cover
+    ssl = None
+
+from . import protocols
+from . import transports
+from .log import logger
+
+
+def _create_transport_context(server_side, server_hostname):
+    if server_side:
+        raise ValueError('Server side SSL needs a valid SSLContext')
+
+    # Client side may pass ssl=True to use a default
+    # context; in that case the sslcontext passed is None.
+    # The default is secure for client connections.
+    if hasattr(ssl, 'create_default_context'):
+        # Python 3.4+: use up-to-date strong settings.
+        sslcontext = ssl.create_default_context()
+        if not server_hostname:
+            sslcontext.check_hostname = False
+    else:
+        # Fallback for Python 3.3.
+        sslcontext = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+        sslcontext.options |= ssl.OP_NO_SSLv2
+        sslcontext.options |= ssl.OP_NO_SSLv3
+        sslcontext.set_default_verify_paths()
+        sslcontext.verify_mode = ssl.CERT_REQUIRED
+    return sslcontext
+
+
+def _is_sslproto_available():
+    return hasattr(ssl, "MemoryBIO")
+
+
+# States of an _SSLPipe.
+_UNWRAPPED = "UNWRAPPED"
+_DO_HANDSHAKE = "DO_HANDSHAKE"
+_WRAPPED = "WRAPPED"
+_SHUTDOWN = "SHUTDOWN"
+
+
+class _SSLPipe(object):
+    """An SSL "Pipe".
+
+    An SSL pipe allows you to communicate with an SSL/TLS protocol instance
+    through memory buffers. It can be used to implement a security layer for an
+    existing connection where you don't have access to the connection's file
+    descriptor, or for some reason you don't want to use it.
+
+    An SSL pipe can be in "wrapped" and "unwrapped" mode. In unwrapped mode,
+    data is passed through untransformed. In wrapped mode, application level
+    data is encrypted to SSL record level data and vice versa. The SSL record
+    level is the lowest level in the SSL protocol suite and is what travels
+    as-is over the wire.
+
+    An SslPipe initially is in "unwrapped" mode. To start SSL, call
+    do_handshake(). To shutdown SSL again, call unwrap().
+    """
+
+    max_size = 256 * 1024   # Buffer size passed to read()
+
+    def __init__(self, context, server_side, server_hostname=None):
+        """
+        The *context* argument specifies the ssl.SSLContext to use.
+
+        The *server_side* argument indicates whether this is a server side or
+        client side transport.
+
+        The optional *server_hostname* argument can be used to specify the
+        hostname you are connecting to. You may only specify this parameter if
+        the _ssl module supports Server Name Indication (SNI).
+        """
+        self._context = context
+        self._server_side = server_side
+        self._server_hostname = server_hostname
+        self._state = _UNWRAPPED
+        self._incoming = ssl.MemoryBIO()
+        self._outgoing = ssl.MemoryBIO()
+        self._sslobj = None
+        self._need_ssldata = False
+        self._handshake_cb = None
+        self._shutdown_cb = None
+
+    @property
+    def context(self):
+        """The SSL context passed to the constructor."""
+        return self._context
+
+    @property
+    def ssl_object(self):
+        """The internal ssl.SSLObject instance.
+
+        Return None if the pipe is not wrapped.
+        """
+        return self._sslobj
+
+    @property
+    def need_ssldata(self):
+        """Whether more record level data is needed to complete a handshake
+        that is currently in progress."""
+        return self._need_ssldata
+
+    @property
+    def wrapped(self):
+        """
+        Whether a security layer is currently in effect.
+
+        Return False during handshake.
+        """
+        return self._state == _WRAPPED
+
+    def do_handshake(self, callback=None):
+        """Start the SSL handshake.
+
+        Return a list of ssldata. A ssldata element is a list of buffers
+
+        The optional *callback* argument can be used to install a callback that
+        will be called when the handshake is complete. The callback will be
+        called with None if successful, else an exception instance.
+        """
+        if self._state != _UNWRAPPED:
+            raise RuntimeError('handshake in progress or completed')
+        self._sslobj = self._context.wrap_bio(
+            self._incoming, self._outgoing,
+            server_side=self._server_side,
+            server_hostname=self._server_hostname)
+        self._state = _DO_HANDSHAKE
+        self._handshake_cb = callback
+        ssldata, appdata = self.feed_ssldata(b'', only_handshake=True)
+        assert len(appdata) == 0
+        return ssldata
+
+    def shutdown(self, callback=None):
+        """Start the SSL shutdown sequence.
+
+        Return a list of ssldata. A ssldata element is a list of buffers
+
+        The optional *callback* argument can be used to install a callback that
+        will be called when the shutdown is complete. The callback will be
+        called without arguments.
+        """
+        if self._state == _UNWRAPPED:
+            raise RuntimeError('no security layer present')
+        if self._state == _SHUTDOWN:
+            raise RuntimeError('shutdown in progress')
+        assert self._state in (_WRAPPED, _DO_HANDSHAKE)
+        self._state = _SHUTDOWN
+        self._shutdown_cb = callback
+        ssldata, appdata = self.feed_ssldata(b'')
+        assert appdata == [] or appdata == [b'']
+        return ssldata
+
+    def feed_eof(self):
+        """Send a potentially "ragged" EOF.
+
+        This method will raise an SSL_ERROR_EOF exception if the EOF is
+        unexpected.
+        """
+        self._incoming.write_eof()
+        ssldata, appdata = self.feed_ssldata(b'')
+        assert appdata == [] or appdata == [b'']
+
+    def feed_ssldata(self, data, only_handshake=False):
+        """Feed SSL record level data into the pipe.
+
+        The data must be a bytes instance. It is OK to send an empty bytes
+        instance. This can be used to get ssldata for a handshake initiated by
+        this endpoint.
+
+        Return a (ssldata, appdata) tuple. The ssldata element is a list of
+        buffers containing SSL data that needs to be sent to the remote SSL.
+
+        The appdata element is a list of buffers containing plaintext data that
+        needs to be forwarded to the application. The appdata list may contain
+        an empty buffer indicating an SSL "close_notify" alert. This alert must
+        be acknowledged by calling shutdown().
+        """
+        if self._state == _UNWRAPPED:
+            # If unwrapped, pass plaintext data straight through.
+            if data:
+                appdata = [data]
+            else:
+                appdata = []
+            return ([], appdata)
+
+        self._need_ssldata = False
+        if data:
+            self._incoming.write(data)
+
+        ssldata = []
+        appdata = []
+        try:
+            if self._state == _DO_HANDSHAKE:
+                # Call do_handshake() until it doesn't raise anymore.
+                self._sslobj.do_handshake()
+                self._state = _WRAPPED
+                if self._handshake_cb:
+                    self._handshake_cb(None)
+                if only_handshake:
+                    return (ssldata, appdata)
+                # Handshake done: execute the wrapped block
+
+            if self._state == _WRAPPED:
+                # Main state: read data from SSL until close_notify
+                while True:
+                    chunk = self._sslobj.read(self.max_size)
+                    appdata.append(chunk)
+                    if not chunk:  # close_notify
+                        break
+
+            elif self._state == _SHUTDOWN:
+                # Call shutdown() until it doesn't raise anymore.
+                self._sslobj.unwrap()
+                self._sslobj = None
+                self._state = _UNWRAPPED
+                if self._shutdown_cb:
+                    self._shutdown_cb()
+
+            elif self._state == _UNWRAPPED:
+                # Drain possible plaintext data after close_notify.
+                appdata.append(self._incoming.read())
+        except (ssl.SSLError, ssl.CertificateError) as exc:
+            if getattr(exc, 'errno', None) not in (
+                    ssl.SSL_ERROR_WANT_READ, ssl.SSL_ERROR_WANT_WRITE,
+                    ssl.SSL_ERROR_SYSCALL):
+                if self._state == _DO_HANDSHAKE and self._handshake_cb:
+                    self._handshake_cb(exc)
+                raise
+            self._need_ssldata = (exc.errno == ssl.SSL_ERROR_WANT_READ)
+
+        # Check for record level data that needs to be sent back.
+        # Happens for the initial handshake and renegotiations.
+        if self._outgoing.pending:
+            ssldata.append(self._outgoing.read())
+        return (ssldata, appdata)
+
+    def feed_appdata(self, data, offset=0):
+        """Feed plaintext data into the pipe.
+
+        Return an (ssldata, offset) tuple. The ssldata element is a list of
+        buffers containing record level data that needs to be sent to the
+        remote SSL instance. The offset is the number of plaintext bytes that
+        were processed, which may be less than the length of data.
+
+        NOTE: In case of short writes, this call MUST be retried with the SAME
+        buffer passed into the *data* argument (i.e. the id() must be the
+        same). This is an OpenSSL requirement. A further particularity is that
+        a short write will always have offset == 0, because the _ssl module
+        does not enable partial writes. And even though the offset is zero,
+        there will still be encrypted data in ssldata.
+        """
+        assert 0 <= offset <= len(data)
+        if self._state == _UNWRAPPED:
+            # pass through data in unwrapped mode
+            if offset < len(data):
+                ssldata = [data[offset:]]
+            else:
+                ssldata = []
+            return (ssldata, len(data))
+
+        ssldata = []
+        view = memoryview(data)
+        while True:
+            self._need_ssldata = False
+            try:
+                if offset < len(view):
+                    offset += self._sslobj.write(view[offset:])
+            except ssl.SSLError as exc:
+                # It is not allowed to call write() after unwrap() until the
+                # close_notify is acknowledged. We return the condition to the
+                # caller as a short write.
+                if exc.reason == 'PROTOCOL_IS_SHUTDOWN':
+                    exc.errno = ssl.SSL_ERROR_WANT_READ
+                if exc.errno not in (ssl.SSL_ERROR_WANT_READ,
+                                     ssl.SSL_ERROR_WANT_WRITE,
+                                     ssl.SSL_ERROR_SYSCALL):
+                    raise
+                self._need_ssldata = (exc.errno == ssl.SSL_ERROR_WANT_READ)
+
+            # See if there's any record level data back for us.
+            if self._outgoing.pending:
+                ssldata.append(self._outgoing.read())
+            if offset == len(view) or self._need_ssldata:
+                break
+        return (ssldata, offset)
+
+
+class _SSLProtocolTransport(transports._FlowControlMixin,
+                            transports.Transport):
+
+    def __init__(self, loop, ssl_protocol, app_protocol):
+        self._loop = loop
+        self._ssl_protocol = ssl_protocol
+        self._app_protocol = app_protocol
+        self._closed = False
+
+    def get_extra_info(self, name, default=None):
+        """Get optional transport information."""
+        return self._ssl_protocol._get_extra_info(name, default)
+
+    def close(self):
+        """Close the transport.
+
+        Buffered data will be flushed asynchronously.  No more data
+        will be received.  After all buffered data is flushed, the
+        protocol's connection_lost() method will (eventually) called
+        with None as its argument.
+        """
+        self._closed = True
+        self._ssl_protocol._start_shutdown()
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if not self._closed:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self.close()
+
+    def pause_reading(self):
+        """Pause the receiving end.
+
+        No data will be passed to the protocol's data_received()
+        method until resume_reading() is called.
+        """
+        self._ssl_protocol._transport.pause_reading()
+
+    def resume_reading(self):
+        """Resume the receiving end.
+
+        Data received will once again be passed to the protocol's
+        data_received() method.
+        """
+        self._ssl_protocol._transport.resume_reading()
+
+    def set_write_buffer_limits(self, high=None, low=None):
+        """Set the high- and low-water limits for write flow control.
+
+        These two values control when to call the protocol's
+        pause_writing() and resume_writing() methods.  If specified,
+        the low-water limit must be less than or equal to the
+        high-water limit.  Neither value can be negative.
+
+        The defaults are implementation-specific.  If only the
+        high-water limit is given, the low-water limit defaults to a
+        implementation-specific value less than or equal to the
+        high-water limit.  Setting high to zero forces low to zero as
+        well, and causes pause_writing() to be called whenever the
+        buffer becomes non-empty.  Setting low to zero causes
+        resume_writing() to be called only once the buffer is empty.
+        Use of zero for either limit is generally sub-optimal as it
+        reduces opportunities for doing I/O and computation
+        concurrently.
+        """
+        self._ssl_protocol._transport.set_write_buffer_limits(high, low)
+
+    def get_write_buffer_size(self):
+        """Return the current size of the write buffer."""
+        return self._ssl_protocol._transport.get_write_buffer_size()
+
+    def write(self, data):
+        """Write some data bytes to the transport.
+
+        This does not block; it buffers the data and arranges for it
+        to be sent out asynchronously.
+        """
+        if not isinstance(data, (bytes, bytearray, memoryview)):
+            raise TypeError("data: expecting a bytes-like instance, got {!r}"
+                                .format(type(data).__name__))
+        if not data:
+            return
+        self._ssl_protocol._write_appdata(data)
+
+    def can_write_eof(self):
+        """Return True if this transport supports write_eof(), False if not."""
+        return False
+
+    def abort(self):
+        """Close the transport immediately.
+
+        Buffered data will be lost.  No more data will be received.
+        The protocol's connection_lost() method will (eventually) be
+        called with None as its argument.
+        """
+        self._ssl_protocol._abort()
+
+
+class SSLProtocol(protocols.Protocol):
+    """SSL protocol.
+
+    Implementation of SSL on top of a socket using incoming and outgoing
+    buffers which are ssl.MemoryBIO objects.
+    """
+
+    def __init__(self, loop, app_protocol, sslcontext, waiter,
+                 server_side=False, server_hostname=None):
+        if ssl is None:
+            raise RuntimeError('stdlib ssl module not available')
+
+        if not sslcontext:
+            sslcontext = _create_transport_context(server_side, server_hostname)
+
+        self._server_side = server_side
+        if server_hostname and not server_side:
+            self._server_hostname = server_hostname
+        else:
+            self._server_hostname = None
+        self._sslcontext = sslcontext
+        # SSL-specific extra info. More info are set when the handshake
+        # completes.
+        self._extra = dict(sslcontext=sslcontext)
+
+        # App data write buffering
+        self._write_backlog = collections.deque()
+        self._write_buffer_size = 0
+
+        self._waiter = waiter
+        self._loop = loop
+        self._app_protocol = app_protocol
+        self._app_transport = _SSLProtocolTransport(self._loop,
+                                                    self, self._app_protocol)
+        self._sslpipe = None
+        self._session_established = False
+        self._in_handshake = False
+        self._in_shutdown = False
+        self._transport = None
+
+    def _wakeup_waiter(self, exc=None):
+        if self._waiter is None:
+            return
+        if not self._waiter.cancelled():
+            if exc is not None:
+                self._waiter.set_exception(exc)
+            else:
+                self._waiter.set_result(None)
+        self._waiter = None
+
+    def connection_made(self, transport):
+        """Called when the low-level connection is made.
+
+        Start the SSL handshake.
+        """
+        self._transport = transport
+        self._sslpipe = _SSLPipe(self._sslcontext,
+                                 self._server_side,
+                                 self._server_hostname)
+        self._start_handshake()
+
+    def connection_lost(self, exc):
+        """Called when the low-level connection is lost or closed.
+
+        The argument is an exception object or None (the latter
+        meaning a regular EOF is received or the connection was
+        aborted or closed).
+        """
+        if self._session_established:
+            self._session_established = False
+            self._loop.call_soon(self._app_protocol.connection_lost, exc)
+        self._transport = None
+        self._app_transport = None
+
+    def pause_writing(self):
+        """Called when the low-level transport's buffer goes over
+        the high-water mark.
+        """
+        self._app_protocol.pause_writing()
+
+    def resume_writing(self):
+        """Called when the low-level transport's buffer drains below
+        the low-water mark.
+        """
+        self._app_protocol.resume_writing()
+
+    def data_received(self, data):
+        """Called when some SSL data is received.
+
+        The argument is a bytes object.
+        """
+        try:
+            ssldata, appdata = self._sslpipe.feed_ssldata(data)
+        except ssl.SSLError as e:
+            if self._loop.get_debug():
+                logger.warning('%r: SSL error %s (reason %s)',
+                               self, e.errno, e.reason)
+            self._abort()
+            return
+
+        for chunk in ssldata:
+            self._transport.write(chunk)
+
+        for chunk in appdata:
+            if chunk:
+                self._app_protocol.data_received(chunk)
+            else:
+                self._start_shutdown()
+                break
+
+    def eof_received(self):
+        """Called when the other end of the low-level stream
+        is half-closed.
+
+        If this returns a false value (including None), the transport
+        will close itself.  If it returns a true value, closing the
+        transport is up to the protocol.
+        """
+        try:
+            if self._loop.get_debug():
+                logger.debug("%r received EOF", self)
+
+            self._wakeup_waiter(ConnectionResetError)
+
+            if not self._in_handshake:
+                keep_open = self._app_protocol.eof_received()
+                if keep_open:
+                    logger.warning('returning true from eof_received() '
+                                   'has no effect when using ssl')
+        finally:
+            self._transport.close()
+
+    def _get_extra_info(self, name, default=None):
+        if name in self._extra:
+            return self._extra[name]
+        else:
+            return self._transport.get_extra_info(name, default)
+
+    def _start_shutdown(self):
+        if self._in_shutdown:
+            return
+        self._in_shutdown = True
+        self._write_appdata(b'')
+
+    def _write_appdata(self, data):
+        self._write_backlog.append((data, 0))
+        self._write_buffer_size += len(data)
+        self._process_write_backlog()
+
+    def _start_handshake(self):
+        if self._loop.get_debug():
+            logger.debug("%r starts SSL handshake", self)
+            self._handshake_start_time = self._loop.time()
+        else:
+            self._handshake_start_time = None
+        self._in_handshake = True
+        # (b'', 1) is a special value in _process_write_backlog() to do
+        # the SSL handshake
+        self._write_backlog.append((b'', 1))
+        self._loop.call_soon(self._process_write_backlog)
+
+    def _on_handshake_complete(self, handshake_exc):
+        self._in_handshake = False
+
+        sslobj = self._sslpipe.ssl_object
+        try:
+            if handshake_exc is not None:
+                raise handshake_exc
+
+            peercert = sslobj.getpeercert()
+            if not hasattr(self._sslcontext, 'check_hostname'):
+                # Verify hostname if requested, Python 3.4+ uses check_hostname
+                # and checks the hostname in do_handshake()
+                if (self._server_hostname
+                and self._sslcontext.verify_mode != ssl.CERT_NONE):
+                    ssl.match_hostname(peercert, self._server_hostname)
+        except BaseException as exc:
+            if self._loop.get_debug():
+                if isinstance(exc, ssl.CertificateError):
+                    logger.warning("%r: SSL handshake failed "
+                                   "on verifying the certificate",
+                                   self, exc_info=True)
+                else:
+                    logger.warning("%r: SSL handshake failed",
+                                   self, exc_info=True)
+            self._transport.close()
+            if isinstance(exc, Exception):
+                self._wakeup_waiter(exc)
+                return
+            else:
+                raise
+
+        if self._loop.get_debug():
+            dt = self._loop.time() - self._handshake_start_time
+            logger.debug("%r: SSL handshake took %.1f ms", self, dt * 1e3)
+
+        # Add extra info that becomes available after handshake.
+        self._extra.update(peercert=peercert,
+                           cipher=sslobj.cipher(),
+                           compression=sslobj.compression(),
+                           )
+        self._app_protocol.connection_made(self._app_transport)
+        self._wakeup_waiter()
+        self._session_established = True
+        # In case transport.write() was already called. Don't call
+        # immediatly _process_write_backlog(), but schedule it:
+        # _on_handshake_complete() can be called indirectly from
+        # _process_write_backlog(), and _process_write_backlog() is not
+        # reentrant.
+        self._loop.call_soon(self._process_write_backlog)
+
+    def _process_write_backlog(self):
+        # Try to make progress on the write backlog.
+        if self._transport is None:
+            return
+
+        try:
+            for i in range(len(self._write_backlog)):
+                data, offset = self._write_backlog[0]
+                if data:
+                    ssldata, offset = self._sslpipe.feed_appdata(data, offset)
+                elif offset:
+                    ssldata = self._sslpipe.do_handshake(self._on_handshake_complete)
+                    offset = 1
+                else:
+                    ssldata = self._sslpipe.shutdown(self._finalize)
+                    offset = 1
+
+                for chunk in ssldata:
+                    self._transport.write(chunk)
+
+                if offset < len(data):
+                    self._write_backlog[0] = (data, offset)
+                    # A short write means that a write is blocked on a read
+                    # We need to enable reading if it is paused!
+                    assert self._sslpipe.need_ssldata
+                    if self._transport._paused:
+                        self._transport.resume_reading()
+                    break
+
+                # An entire chunk from the backlog was processed. We can
+                # delete it and reduce the outstanding buffer size.
+                del self._write_backlog[0]
+                self._write_buffer_size -= len(data)
+        except BaseException as exc:
+            if self._in_handshake:
+                self._on_handshake_complete(exc)
+            else:
+                self._fatal_error(exc, 'Fatal error on SSL transport')
+
+    def _fatal_error(self, exc, message='Fatal error on transport'):
+        # Should be called from exception handler only.
+        if isinstance(exc, (BrokenPipeError, ConnectionResetError)):
+            if self._loop.get_debug():
+                logger.debug("%r: %s", self, message, exc_info=True)
+        else:
+            self._loop.call_exception_handler({
+                'message': message,
+                'exception': exc,
+                'transport': self._transport,
+                'protocol': self,
+            })
+        if self._transport:
+            self._transport._force_close(exc)
+
+    def _finalize(self):
+        if self._transport is not None:
+            self._transport.close()
+
+    def _abort(self):
+        if self._transport is not None:
+            try:
+                self._transport.abort()
+            finally:
+                self._finalize()
diff --git a/trollius/streams.py b/trollius/streams.py
new file mode 100644
index 0000000..176c65e
--- /dev/null
+++ b/trollius/streams.py
@@ -0,0 +1,501 @@
+"""Stream-related things."""
+
+__all__ = ['StreamReader', 'StreamWriter', 'StreamReaderProtocol',
+           'open_connection', 'start_server',
+           'IncompleteReadError',
+           ]
+
+import socket
+import sys
+
+if hasattr(socket, 'AF_UNIX'):
+    __all__.extend(['open_unix_connection', 'start_unix_server'])
+
+from . import coroutines
+from . import events
+from . import futures
+from . import protocols
+from .coroutines import coroutine
+from .log import logger
+
+
+_DEFAULT_LIMIT = 2**16
+_PY35 = sys.version_info >= (3, 5)
+
+
+class IncompleteReadError(EOFError):
+    """
+    Incomplete read error. Attributes:
+
+    - partial: read bytes string before the end of stream was reached
+    - expected: total number of expected bytes
+    """
+    def __init__(self, partial, expected):
+        EOFError.__init__(self, "%s bytes read on a total of %s expected bytes"
+                                % (len(partial), expected))
+        self.partial = partial
+        self.expected = expected
+
+
+@coroutine
+def open_connection(host=None, port=None, *,
+                    loop=None, limit=_DEFAULT_LIMIT, **kwds):
+    """A wrapper for create_connection() returning a (reader, writer) pair.
+
+    The reader returned is a StreamReader instance; the writer is a
+    StreamWriter instance.
+
+    The arguments are all the usual arguments to create_connection()
+    except protocol_factory; most common are positional host and port,
+    with various optional keyword arguments following.
+
+    Additional optional keyword arguments are loop (to set the event loop
+    instance to use) and limit (to set the buffer limit passed to the
+    StreamReader).
+
+    (If you want to customize the StreamReader and/or
+    StreamReaderProtocol classes, just copy the code -- there's
+    really nothing special here except some convenience.)
+    """
+    if loop is None:
+        loop = events.get_event_loop()
+    reader = StreamReader(limit=limit, loop=loop)
+    protocol = StreamReaderProtocol(reader, loop=loop)
+    transport, _ = yield from loop.create_connection(
+        lambda: protocol, host, port, **kwds)
+    writer = StreamWriter(transport, protocol, reader, loop)
+    return reader, writer
+
+
+@coroutine
+def start_server(client_connected_cb, host=None, port=None, *,
+                 loop=None, limit=_DEFAULT_LIMIT, **kwds):
+    """Start a socket server, call back for each client connected.
+
+    The first parameter, `client_connected_cb`, takes two parameters:
+    client_reader, client_writer.  client_reader is a StreamReader
+    object, while client_writer is a StreamWriter object.  This
+    parameter can either be a plain callback function or a coroutine;
+    if it is a coroutine, it will be automatically converted into a
+    Task.
+
+    The rest of the arguments are all the usual arguments to
+    loop.create_server() except protocol_factory; most common are
+    positional host and port, with various optional keyword arguments
+    following.  The return value is the same as loop.create_server().
+
+    Additional optional keyword arguments are loop (to set the event loop
+    instance to use) and limit (to set the buffer limit passed to the
+    StreamReader).
+
+    The return value is the same as loop.create_server(), i.e. a
+    Server object which can be used to stop the service.
+    """
+    if loop is None:
+        loop = events.get_event_loop()
+
+    def factory():
+        reader = StreamReader(limit=limit, loop=loop)
+        protocol = StreamReaderProtocol(reader, client_connected_cb,
+                                        loop=loop)
+        return protocol
+
+    return (yield from loop.create_server(factory, host, port, **kwds))
+
+
+if hasattr(socket, 'AF_UNIX'):
+    # UNIX Domain Sockets are supported on this platform
+
+    @coroutine
+    def open_unix_connection(path=None, *,
+                             loop=None, limit=_DEFAULT_LIMIT, **kwds):
+        """Similar to `open_connection` but works with UNIX Domain Sockets."""
+        if loop is None:
+            loop = events.get_event_loop()
+        reader = StreamReader(limit=limit, loop=loop)
+        protocol = StreamReaderProtocol(reader, loop=loop)
+        transport, _ = yield from loop.create_unix_connection(
+            lambda: protocol, path, **kwds)
+        writer = StreamWriter(transport, protocol, reader, loop)
+        return reader, writer
+
+
+    @coroutine
+    def start_unix_server(client_connected_cb, path=None, *,
+                          loop=None, limit=_DEFAULT_LIMIT, **kwds):
+        """Similar to `start_server` but works with UNIX Domain Sockets."""
+        if loop is None:
+            loop = events.get_event_loop()
+
+        def factory():
+            reader = StreamReader(limit=limit, loop=loop)
+            protocol = StreamReaderProtocol(reader, client_connected_cb,
+                                            loop=loop)
+            return protocol
+
+        return (yield from loop.create_unix_server(factory, path, **kwds))
+
+
+class FlowControlMixin(protocols.Protocol):
+    """Reusable flow control logic for StreamWriter.drain().
+
+    This implements the protocol methods pause_writing(),
+    resume_reading() and connection_lost().  If the subclass overrides
+    these it must call the super methods.
+
+    StreamWriter.drain() must wait for _drain_helper() coroutine.
+    """
+
+    def __init__(self, loop=None):
+        if loop is None:
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
+        self._paused = False
+        self._drain_waiter = None
+        self._connection_lost = False
+
+    def pause_writing(self):
+        assert not self._paused
+        self._paused = True
+        if self._loop.get_debug():
+            logger.debug("%r pauses writing", self)
+
+    def resume_writing(self):
+        assert self._paused
+        self._paused = False
+        if self._loop.get_debug():
+            logger.debug("%r resumes writing", self)
+
+        waiter = self._drain_waiter
+        if waiter is not None:
+            self._drain_waiter = None
+            if not waiter.done():
+                waiter.set_result(None)
+
+    def connection_lost(self, exc):
+        self._connection_lost = True
+        # Wake up the writer if currently paused.
+        if not self._paused:
+            return
+        waiter = self._drain_waiter
+        if waiter is None:
+            return
+        self._drain_waiter = None
+        if waiter.done():
+            return
+        if exc is None:
+            waiter.set_result(None)
+        else:
+            waiter.set_exception(exc)
+
+    @coroutine
+    def _drain_helper(self):
+        if self._connection_lost:
+            raise ConnectionResetError('Connection lost')
+        if not self._paused:
+            return
+        waiter = self._drain_waiter
+        assert waiter is None or waiter.cancelled()
+        waiter = futures.Future(loop=self._loop)
+        self._drain_waiter = waiter
+        yield from waiter
+
+
+class StreamReaderProtocol(FlowControlMixin, protocols.Protocol):
+    """Helper class to adapt between Protocol and StreamReader.
+
+    (This is a helper class instead of making StreamReader itself a
+    Protocol subclass, because the StreamReader has other potential
+    uses, and to prevent the user of the StreamReader to accidentally
+    call inappropriate methods of the protocol.)
+    """
+
+    def __init__(self, stream_reader, client_connected_cb=None, loop=None):
+        super().__init__(loop=loop)
+        self._stream_reader = stream_reader
+        self._stream_writer = None
+        self._client_connected_cb = client_connected_cb
+
+    def connection_made(self, transport):
+        self._stream_reader.set_transport(transport)
+        if self._client_connected_cb is not None:
+            self._stream_writer = StreamWriter(transport, self,
+                                               self._stream_reader,
+                                               self._loop)
+            res = self._client_connected_cb(self._stream_reader,
+                                            self._stream_writer)
+            if coroutines.iscoroutine(res):
+                self._loop.create_task(res)
+
+    def connection_lost(self, exc):
+        if exc is None:
+            self._stream_reader.feed_eof()
+        else:
+            self._stream_reader.set_exception(exc)
+        super().connection_lost(exc)
+
+    def data_received(self, data):
+        self._stream_reader.feed_data(data)
+
+    def eof_received(self):
+        self._stream_reader.feed_eof()
+
+
+class StreamWriter:
+    """Wraps a Transport.
+
+    This exposes write(), writelines(), [can_]write_eof(),
+    get_extra_info() and close().  It adds drain() which returns an
+    optional Future on which you can wait for flow control.  It also
+    adds a transport property which references the Transport
+    directly.
+    """
+
+    def __init__(self, transport, protocol, reader, loop):
+        self._transport = transport
+        self._protocol = protocol
+        # drain() expects that the reader has a exception() method
+        assert reader is None or isinstance(reader, StreamReader)
+        self._reader = reader
+        self._loop = loop
+
+    def __repr__(self):
+        info = [self.__class__.__name__, 'transport=%r' % self._transport]
+        if self._reader is not None:
+            info.append('reader=%r' % self._reader)
+        return '<%s>' % ' '.join(info)
+
+    @property
+    def transport(self):
+        return self._transport
+
+    def write(self, data):
+        self._transport.write(data)
+
+    def writelines(self, data):
+        self._transport.writelines(data)
+
+    def write_eof(self):
+        return self._transport.write_eof()
+
+    def can_write_eof(self):
+        return self._transport.can_write_eof()
+
+    def close(self):
+        return self._transport.close()
+
+    def get_extra_info(self, name, default=None):
+        return self._transport.get_extra_info(name, default)
+
+    @coroutine
+    def drain(self):
+        """Flush the write buffer.
+
+        The intended use is to write
+
+          w.write(data)
+          yield from w.drain()
+        """
+        if self._reader is not None:
+            exc = self._reader.exception()
+            if exc is not None:
+                raise exc
+        yield from self._protocol._drain_helper()
+
+
+class StreamReader:
+
+    def __init__(self, limit=_DEFAULT_LIMIT, loop=None):
+        # The line length limit is  a security feature;
+        # it also doubles as half the buffer limit.
+        self._limit = limit
+        if loop is None:
+            self._loop = events.get_event_loop()
+        else:
+            self._loop = loop
+        self._buffer = bytearray()
+        self._eof = False    # Whether we're done.
+        self._waiter = None  # A future used by _wait_for_data()
+        self._exception = None
+        self._transport = None
+        self._paused = False
+
+    def exception(self):
+        return self._exception
+
+    def set_exception(self, exc):
+        self._exception = exc
+
+        waiter = self._waiter
+        if waiter is not None:
+            self._waiter = None
+            if not waiter.cancelled():
+                waiter.set_exception(exc)
+
+    def _wakeup_waiter(self):
+        """Wakeup read() or readline() function waiting for data or EOF."""
+        waiter = self._waiter
+        if waiter is not None:
+            self._waiter = None
+            if not waiter.cancelled():
+                waiter.set_result(None)
+
+    def set_transport(self, transport):
+        assert self._transport is None, 'Transport already set'
+        self._transport = transport
+
+    def _maybe_resume_transport(self):
+        if self._paused and len(self._buffer) <= self._limit:
+            self._paused = False
+            self._transport.resume_reading()
+
+    def feed_eof(self):
+        self._eof = True
+        self._wakeup_waiter()
+
+    def at_eof(self):
+        """Return True if the buffer is empty and 'feed_eof' was called."""
+        return self._eof and not self._buffer
+
+    def feed_data(self, data):
+        assert not self._eof, 'feed_data after feed_eof'
+
+        if not data:
+            return
+
+        self._buffer.extend(data)
+        self._wakeup_waiter()
+
+        if (self._transport is not None and
+            not self._paused and
+            len(self._buffer) > 2*self._limit):
+            try:
+                self._transport.pause_reading()
+            except NotImplementedError:
+                # The transport can't be paused.
+                # We'll just have to buffer all data.
+                # Forget the transport so we don't keep trying.
+                self._transport = None
+            else:
+                self._paused = True
+
+    @coroutine
+    def _wait_for_data(self, func_name):
+        """Wait until feed_data() or feed_eof() is called."""
+        # StreamReader uses a future to link the protocol feed_data() method
+        # to a read coroutine. Running two read coroutines at the same time
+        # would have an unexpected behaviour. It would not possible to know
+        # which coroutine would get the next data.
+        if self._waiter is not None:
+            raise RuntimeError('%s() called while another coroutine is '
+                               'already waiting for incoming data' % func_name)
+
+        self._waiter = futures.Future(loop=self._loop)
+        try:
+            yield from self._waiter
+        finally:
+            self._waiter = None
+
+    @coroutine
+    def readline(self):
+        if self._exception is not None:
+            raise self._exception
+
+        line = bytearray()
+        not_enough = True
+
+        while not_enough:
+            while self._buffer and not_enough:
+                ichar = self._buffer.find(b'\n')
+                if ichar < 0:
+                    line.extend(self._buffer)
+                    self._buffer.clear()
+                else:
+                    ichar += 1
+                    line.extend(self._buffer[:ichar])
+                    del self._buffer[:ichar]
+                    not_enough = False
+
+                if len(line) > self._limit:
+                    self._maybe_resume_transport()
+                    raise ValueError('Line is too long')
+
+            if self._eof:
+                break
+
+            if not_enough:
+                yield from self._wait_for_data('readline')
+
+        self._maybe_resume_transport()
+        return bytes(line)
+
+    @coroutine
+    def read(self, n=-1):
+        if self._exception is not None:
+            raise self._exception
+
+        if not n:
+            return b''
+
+        if n < 0:
+            # This used to just loop creating a new waiter hoping to
+            # collect everything in self._buffer, but that would
+            # deadlock if the subprocess sends more than self.limit
+            # bytes.  So just call self.read(self._limit) until EOF.
+            blocks = []
+            while True:
+                block = yield from self.read(self._limit)
+                if not block:
+                    break
+                blocks.append(block)
+            return b''.join(blocks)
+        else:
+            if not self._buffer and not self._eof:
+                yield from self._wait_for_data('read')
+
+        if n < 0 or len(self._buffer) <= n:
+            data = bytes(self._buffer)
+            self._buffer.clear()
+        else:
+            # n > 0 and len(self._buffer) > n
+            data = bytes(self._buffer[:n])
+            del self._buffer[:n]
+
+        self._maybe_resume_transport()
+        return data
+
+    @coroutine
+    def readexactly(self, n):
+        if self._exception is not None:
+            raise self._exception
+
+        # There used to be "optimized" code here.  It created its own
+        # Future and waited until self._buffer had at least the n
+        # bytes, then called read(n).  Unfortunately, this could pause
+        # the transport if the argument was larger than the pause
+        # limit (which is twice self._limit).  So now we just read()
+        # into a local buffer.
+
+        blocks = []
+        while n > 0:
+            block = yield from self.read(n)
+            if not block:
+                partial = b''.join(blocks)
+                raise IncompleteReadError(partial, len(partial) + n)
+            blocks.append(block)
+            n -= len(block)
+
+        return b''.join(blocks)
+
+    if _PY35:
+        @coroutine
+        def __aiter__(self):
+            return self
+
+        @coroutine
+        def __anext__(self):
+            val = yield from self.readline()
+            if val == b'':
+                raise StopAsyncIteration
+            return val
diff --git a/trollius/subprocess.py b/trollius/subprocess.py
new file mode 100644
index 0000000..4600a9f
--- /dev/null
+++ b/trollius/subprocess.py
@@ -0,0 +1,215 @@
+__all__ = ['create_subprocess_exec', 'create_subprocess_shell']
+
+import collections
+import subprocess
+
+from . import events
+from . import futures
+from . import protocols
+from . import streams
+from . import tasks
+from .coroutines import coroutine
+from .log import logger
+
+
+PIPE = subprocess.PIPE
+STDOUT = subprocess.STDOUT
+DEVNULL = subprocess.DEVNULL
+
+
+class SubprocessStreamProtocol(streams.FlowControlMixin,
+                               protocols.SubprocessProtocol):
+    """Like StreamReaderProtocol, but for a subprocess."""
+
+    def __init__(self, limit, loop):
+        super().__init__(loop=loop)
+        self._limit = limit
+        self.stdin = self.stdout = self.stderr = None
+        self._transport = None
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self.stdin is not None:
+            info.append('stdin=%r' % self.stdin)
+        if self.stdout is not None:
+            info.append('stdout=%r' % self.stdout)
+        if self.stderr is not None:
+            info.append('stderr=%r' % self.stderr)
+        return '<%s>' % ' '.join(info)
+
+    def connection_made(self, transport):
+        self._transport = transport
+
+        stdout_transport = transport.get_pipe_transport(1)
+        if stdout_transport is not None:
+            self.stdout = streams.StreamReader(limit=self._limit,
+                                               loop=self._loop)
+            self.stdout.set_transport(stdout_transport)
+
+        stderr_transport = transport.get_pipe_transport(2)
+        if stderr_transport is not None:
+            self.stderr = streams.StreamReader(limit=self._limit,
+                                               loop=self._loop)
+            self.stderr.set_transport(stderr_transport)
+
+        stdin_transport = transport.get_pipe_transport(0)
+        if stdin_transport is not None:
+            self.stdin = streams.StreamWriter(stdin_transport,
+                                              protocol=self,
+                                              reader=None,
+                                              loop=self._loop)
+
+    def pipe_data_received(self, fd, data):
+        if fd == 1:
+            reader = self.stdout
+        elif fd == 2:
+            reader = self.stderr
+        else:
+            reader = None
+        if reader is not None:
+            reader.feed_data(data)
+
+    def pipe_connection_lost(self, fd, exc):
+        if fd == 0:
+            pipe = self.stdin
+            if pipe is not None:
+                pipe.close()
+            self.connection_lost(exc)
+            return
+        if fd == 1:
+            reader = self.stdout
+        elif fd == 2:
+            reader = self.stderr
+        else:
+            reader = None
+        if reader != None:
+            if exc is None:
+                reader.feed_eof()
+            else:
+                reader.set_exception(exc)
+
+    def process_exited(self):
+        self._transport.close()
+        self._transport = None
+
+
+class Process:
+    def __init__(self, transport, protocol, loop):
+        self._transport = transport
+        self._protocol = protocol
+        self._loop = loop
+        self.stdin = protocol.stdin
+        self.stdout = protocol.stdout
+        self.stderr = protocol.stderr
+        self.pid = transport.get_pid()
+
+    def __repr__(self):
+        return '<%s %s>' % (self.__class__.__name__, self.pid)
+
+    @property
+    def returncode(self):
+        return self._transport.get_returncode()
+
+    @coroutine
+    def wait(self):
+        """Wait until the process exit and return the process return code.
+
+        This method is a coroutine."""
+        return (yield from self._transport._wait())
+
+    def send_signal(self, signal):
+        self._transport.send_signal(signal)
+
+    def terminate(self):
+        self._transport.terminate()
+
+    def kill(self):
+        self._transport.kill()
+
+    @coroutine
+    def _feed_stdin(self, input):
+        debug = self._loop.get_debug()
+        self.stdin.write(input)
+        if debug:
+            logger.debug('%r communicate: feed stdin (%s bytes)',
+                        self, len(input))
+        try:
+            yield from self.stdin.drain()
+        except (BrokenPipeError, ConnectionResetError) as exc:
+            # communicate() ignores BrokenPipeError and ConnectionResetError
+            if debug:
+                logger.debug('%r communicate: stdin got %r', self, exc)
+
+        if debug:
+            logger.debug('%r communicate: close stdin', self)
+        self.stdin.close()
+
+    @coroutine
+    def _noop(self):
+        return None
+
+    @coroutine
+    def _read_stream(self, fd):
+        transport = self._transport.get_pipe_transport(fd)
+        if fd == 2:
+            stream = self.stderr
+        else:
+            assert fd == 1
+            stream = self.stdout
+        if self._loop.get_debug():
+            name = 'stdout' if fd == 1 else 'stderr'
+            logger.debug('%r communicate: read %s', self, name)
+        output = yield from stream.read()
+        if self._loop.get_debug():
+            name = 'stdout' if fd == 1 else 'stderr'
+            logger.debug('%r communicate: close %s', self, name)
+        transport.close()
+        return output
+
+    @coroutine
+    def communicate(self, input=None):
+        if input:
+            stdin = self._feed_stdin(input)
+        else:
+            stdin = self._noop()
+        if self.stdout is not None:
+            stdout = self._read_stream(1)
+        else:
+            stdout = self._noop()
+        if self.stderr is not None:
+            stderr = self._read_stream(2)
+        else:
+            stderr = self._noop()
+        stdin, stdout, stderr = yield from tasks.gather(stdin, stdout, stderr,
+                                                        loop=self._loop)
+        yield from self.wait()
+        return (stdout, stderr)
+
+
+@coroutine
+def create_subprocess_shell(cmd, stdin=None, stdout=None, stderr=None,
+                            loop=None, limit=streams._DEFAULT_LIMIT, **kwds):
+    if loop is None:
+        loop = events.get_event_loop()
+    protocol_factory = lambda: SubprocessStreamProtocol(limit=limit,
+                                                        loop=loop)
+    transport, protocol = yield from loop.subprocess_shell(
+                                            protocol_factory,
+                                            cmd, stdin=stdin, stdout=stdout,
+                                            stderr=stderr, **kwds)
+    return Process(transport, protocol, loop)
+
+@coroutine
+def create_subprocess_exec(program, *args, stdin=None, stdout=None,
+                           stderr=None, loop=None,
+                           limit=streams._DEFAULT_LIMIT, **kwds):
+    if loop is None:
+        loop = events.get_event_loop()
+    protocol_factory = lambda: SubprocessStreamProtocol(limit=limit,
+                                                        loop=loop)
+    transport, protocol = yield from loop.subprocess_exec(
+                                            protocol_factory,
+                                            program, *args,
+                                            stdin=stdin, stdout=stdout,
+                                            stderr=stderr, **kwds)
+    return Process(transport, protocol, loop)
diff --git a/trollius/tasks.py b/trollius/tasks.py
new file mode 100644
index 0000000..d8193ba
--- /dev/null
+++ b/trollius/tasks.py
@@ -0,0 +1,681 @@
+"""Support for tasks, coroutines and the scheduler."""
+
+__all__ = ['Task',
+           'FIRST_COMPLETED', 'FIRST_EXCEPTION', 'ALL_COMPLETED',
+           'wait', 'wait_for', 'as_completed', 'sleep', 'async',
+           'gather', 'shield', 'ensure_future',
+           ]
+
+import concurrent.futures
+import functools
+import inspect
+import linecache
+import sys
+import types
+import traceback
+import warnings
+import weakref
+
+from . import coroutines
+from . import events
+from . import futures
+from .coroutines import coroutine
+
+_PY34 = (sys.version_info >= (3, 4))
+
+
+class Task(futures.Future):
+    """A coroutine wrapped in a Future."""
+
+    # An important invariant maintained while a Task not done:
+    #
+    # - Either _fut_waiter is None, and _step() is scheduled;
+    # - or _fut_waiter is some Future, and _step() is *not* scheduled.
+    #
+    # The only transition from the latter to the former is through
+    # _wakeup().  When _fut_waiter is not None, one of its callbacks
+    # must be _wakeup().
+
+    # Weak set containing all tasks alive.
+    _all_tasks = weakref.WeakSet()
+
+    # Dictionary containing tasks that are currently active in
+    # all running event loops.  {EventLoop: Task}
+    _current_tasks = {}
+
+    # If False, don't log a message if the task is destroyed whereas its
+    # status is still pending
+    _log_destroy_pending = True
+
+    @classmethod
+    def current_task(cls, loop=None):
+        """Return the currently running task in an event loop or None.
+
+        By default the current task for the current event loop is returned.
+
+        None is returned when called not in the context of a Task.
+        """
+        if loop is None:
+            loop = events.get_event_loop()
+        return cls._current_tasks.get(loop)
+
+    @classmethod
+    def all_tasks(cls, loop=None):
+        """Return a set of all tasks for an event loop.
+
+        By default all tasks for the current event loop are returned.
+        """
+        if loop is None:
+            loop = events.get_event_loop()
+        return {t for t in cls._all_tasks if t._loop is loop}
+
+    def __init__(self, coro, *, loop=None):
+        assert coroutines.iscoroutine(coro), repr(coro)
+        super().__init__(loop=loop)
+        if self._source_traceback:
+            del self._source_traceback[-1]
+        self._coro = coro
+        self._fut_waiter = None
+        self._must_cancel = False
+        self._loop.call_soon(self._step)
+        self.__class__._all_tasks.add(self)
+
+    # On Python 3.3 or older, objects with a destructor that are part of a
+    # reference cycle are never destroyed. That's not the case any more on
+    # Python 3.4 thanks to the PEP 442.
+    if _PY34:
+        def __del__(self):
+            if self._state == futures._PENDING and self._log_destroy_pending:
+                context = {
+                    'task': self,
+                    'message': 'Task was destroyed but it is pending!',
+                }
+                if self._source_traceback:
+                    context['source_traceback'] = self._source_traceback
+                self._loop.call_exception_handler(context)
+            futures.Future.__del__(self)
+
+    def _repr_info(self):
+        info = super()._repr_info()
+
+        if self._must_cancel:
+            # replace status
+            info[0] = 'cancelling'
+
+        coro = coroutines._format_coroutine(self._coro)
+        info.insert(1, 'coro=<%s>' % coro)
+
+        if self._fut_waiter is not None:
+            info.insert(2, 'wait_for=%r' % self._fut_waiter)
+        return info
+
+    def get_stack(self, *, limit=None):
+        """Return the list of stack frames for this task's coroutine.
+
+        If the coroutine is not done, this returns the stack where it is
+        suspended.  If the coroutine has completed successfully or was
+        cancelled, this returns an empty list.  If the coroutine was
+        terminated by an exception, this returns the list of traceback
+        frames.
+
+        The frames are always ordered from oldest to newest.
+
+        The optional limit gives the maximum number of frames to
+        return; by default all available frames are returned.  Its
+        meaning differs depending on whether a stack or a traceback is
+        returned: the newest frames of a stack are returned, but the
+        oldest frames of a traceback are returned.  (This matches the
+        behavior of the traceback module.)
+
+        For reasons beyond our control, only one stack frame is
+        returned for a suspended coroutine.
+        """
+        frames = []
+        f = self._coro.gi_frame
+        if f is not None:
+            while f is not None:
+                if limit is not None:
+                    if limit <= 0:
+                        break
+                    limit -= 1
+                frames.append(f)
+                f = f.f_back
+            frames.reverse()
+        elif self._exception is not None:
+            tb = self._exception.__traceback__
+            while tb is not None:
+                if limit is not None:
+                    if limit <= 0:
+                        break
+                    limit -= 1
+                frames.append(tb.tb_frame)
+                tb = tb.tb_next
+        return frames
+
+    def print_stack(self, *, limit=None, file=None):
+        """Print the stack or traceback for this task's coroutine.
+
+        This produces output similar to that of the traceback module,
+        for the frames retrieved by get_stack().  The limit argument
+        is passed to get_stack().  The file argument is an I/O stream
+        to which the output is written; by default output is written
+        to sys.stderr.
+        """
+        extracted_list = []
+        checked = set()
+        for f in self.get_stack(limit=limit):
+            lineno = f.f_lineno
+            co = f.f_code
+            filename = co.co_filename
+            name = co.co_name
+            if filename not in checked:
+                checked.add(filename)
+                linecache.checkcache(filename)
+            line = linecache.getline(filename, lineno, f.f_globals)
+            extracted_list.append((filename, lineno, name, line))
+        exc = self._exception
+        if not extracted_list:
+            print('No stack for %r' % self, file=file)
+        elif exc is not None:
+            print('Traceback for %r (most recent call last):' % self,
+                  file=file)
+        else:
+            print('Stack for %r (most recent call last):' % self,
+                  file=file)
+        traceback.print_list(extracted_list, file=file)
+        if exc is not None:
+            for line in traceback.format_exception_only(exc.__class__, exc):
+                print(line, file=file, end='')
+
+    def cancel(self):
+        """Request that this task cancel itself.
+
+        This arranges for a CancelledError to be thrown into the
+        wrapped coroutine on the next cycle through the event loop.
+        The coroutine then has a chance to clean up or even deny
+        the request using try/except/finally.
+
+        Unlike Future.cancel, this does not guarantee that the
+        task will be cancelled: the exception might be caught and
+        acted upon, delaying cancellation of the task or preventing
+        cancellation completely.  The task may also return a value or
+        raise a different exception.
+
+        Immediately after this method is called, Task.cancelled() will
+        not return True (unless the task was already cancelled).  A
+        task will be marked as cancelled when the wrapped coroutine
+        terminates with a CancelledError exception (even if cancel()
+        was not called).
+        """
+        if self.done():
+            return False
+        if self._fut_waiter is not None:
+            if self._fut_waiter.cancel():
+                # Leave self._fut_waiter; it may be a Task that
+                # catches and ignores the cancellation so we may have
+                # to cancel it again later.
+                return True
+        # It must be the case that self._step is already scheduled.
+        self._must_cancel = True
+        return True
+
+    def _step(self, value=None, exc=None):
+        assert not self.done(), \
+            '_step(): already done: {!r}, {!r}, {!r}'.format(self, value, exc)
+        if self._must_cancel:
+            if not isinstance(exc, futures.CancelledError):
+                exc = futures.CancelledError()
+            self._must_cancel = False
+        coro = self._coro
+        self._fut_waiter = None
+
+        self.__class__._current_tasks[self._loop] = self
+        # Call either coro.throw(exc) or coro.send(value).
+        try:
+            if exc is not None:
+                result = coro.throw(exc)
+            else:
+                result = coro.send(value)
+        except StopIteration as exc:
+            self.set_result(exc.value)
+        except futures.CancelledError as exc:
+            super().cancel()  # I.e., Future.cancel(self).
+        except Exception as exc:
+            self.set_exception(exc)
+        except BaseException as exc:
+            self.set_exception(exc)
+            raise
+        else:
+            if isinstance(result, futures.Future):
+                # Yielded Future must come from Future.__iter__().
+                if result._blocking:
+                    result._blocking = False
+                    result.add_done_callback(self._wakeup)
+                    self._fut_waiter = result
+                    if self._must_cancel:
+                        if self._fut_waiter.cancel():
+                            self._must_cancel = False
+                else:
+                    self._loop.call_soon(
+                        self._step, None,
+                        RuntimeError(
+                            'yield was used instead of yield from '
+                            'in task {!r} with {!r}'.format(self, result)))
+            elif result is None:
+                # Bare yield relinquishes control for one event loop iteration.
+                self._loop.call_soon(self._step)
+            elif inspect.isgenerator(result):
+                # Yielding a generator is just wrong.
+                self._loop.call_soon(
+                    self._step, None,
+                    RuntimeError(
+                        'yield was used instead of yield from for '
+                        'generator in task {!r} with {}'.format(
+                            self, result)))
+            else:
+                # Yielding something else is an error.
+                self._loop.call_soon(
+                    self._step, None,
+                    RuntimeError(
+                        'Task got bad yield: {!r}'.format(result)))
+        finally:
+            self.__class__._current_tasks.pop(self._loop)
+            self = None  # Needed to break cycles when an exception occurs.
+
+    def _wakeup(self, future):
+        try:
+            value = future.result()
+        except Exception as exc:
+            # This may also be a cancellation.
+            self._step(None, exc)
+        else:
+            self._step(value, None)
+        self = None  # Needed to break cycles when an exception occurs.
+
+
+# wait() and as_completed() similar to those in PEP 3148.
+
+FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
+FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
+ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
+
+
+@coroutine
+def wait(fs, *, loop=None, timeout=None, return_when=ALL_COMPLETED):
+    """Wait for the Futures and coroutines given by fs to complete.
+
+    The sequence futures must not be empty.
+
+    Coroutines will be wrapped in Tasks.
+
+    Returns two sets of Future: (done, pending).
+
+    Usage:
+
+        done, pending = yield from asyncio.wait(fs)
+
+    Note: This does not raise TimeoutError! Futures that aren't done
+    when the timeout occurs are returned in the second set.
+    """
+    if isinstance(fs, futures.Future) or coroutines.iscoroutine(fs):
+        raise TypeError("expect a list of futures, not %s" % type(fs).__name__)
+    if not fs:
+        raise ValueError('Set of coroutines/Futures is empty.')
+    if return_when not in (FIRST_COMPLETED, FIRST_EXCEPTION, ALL_COMPLETED):
+        raise ValueError('Invalid return_when value: {}'.format(return_when))
+
+    if loop is None:
+        loop = events.get_event_loop()
+
+    fs = {ensure_future(f, loop=loop) for f in set(fs)}
+
+    return (yield from _wait(fs, timeout, return_when, loop))
+
+
+def _release_waiter(waiter, *args):
+    if not waiter.done():
+        waiter.set_result(None)
+
+
+@coroutine
+def wait_for(fut, timeout, *, loop=None):
+    """Wait for the single Future or coroutine to complete, with timeout.
+
+    Coroutine will be wrapped in Task.
+
+    Returns result of the Future or coroutine.  When a timeout occurs,
+    it cancels the task and raises TimeoutError.  To avoid the task
+    cancellation, wrap it in shield().
+
+    If the wait is cancelled, the task is also cancelled.
+
+    This function is a coroutine.
+    """
+    if loop is None:
+        loop = events.get_event_loop()
+
+    if timeout is None:
+        return (yield from fut)
+
+    waiter = futures.Future(loop=loop)
+    timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
+    cb = functools.partial(_release_waiter, waiter)
+
+    fut = ensure_future(fut, loop=loop)
+    fut.add_done_callback(cb)
+
+    try:
+        # wait until the future completes or the timeout
+        try:
+            yield from waiter
+        except futures.CancelledError:
+            fut.remove_done_callback(cb)
+            fut.cancel()
+            raise
+
+        if fut.done():
+            return fut.result()
+        else:
+            fut.remove_done_callback(cb)
+            fut.cancel()
+            raise futures.TimeoutError()
+    finally:
+        timeout_handle.cancel()
+
+
+@coroutine
+def _wait(fs, timeout, return_when, loop):
+    """Internal helper for wait() and _wait_for().
+
+    The fs argument must be a collection of Futures.
+    """
+    assert fs, 'Set of Futures is empty.'
+    waiter = futures.Future(loop=loop)
+    timeout_handle = None
+    if timeout is not None:
+        timeout_handle = loop.call_later(timeout, _release_waiter, waiter)
+    counter = len(fs)
+
+    def _on_completion(f):
+        nonlocal counter
+        counter -= 1
+        if (counter <= 0 or
+            return_when == FIRST_COMPLETED or
+            return_when == FIRST_EXCEPTION and (not f.cancelled() and
+                                                f.exception() is not None)):
+            if timeout_handle is not None:
+                timeout_handle.cancel()
+            if not waiter.done():
+                waiter.set_result(None)
+
+    for f in fs:
+        f.add_done_callback(_on_completion)
+
+    try:
+        yield from waiter
+    finally:
+        if timeout_handle is not None:
+            timeout_handle.cancel()
+
+    done, pending = set(), set()
+    for f in fs:
+        f.remove_done_callback(_on_completion)
+        if f.done():
+            done.add(f)
+        else:
+            pending.add(f)
+    return done, pending
+
+
+# This is *not* a @coroutine!  It is just an iterator (yielding Futures).
+def as_completed(fs, *, loop=None, timeout=None):
+    """Return an iterator whose values are coroutines.
+
+    When waiting for the yielded coroutines you'll get the results (or
+    exceptions!) of the original Futures (or coroutines), in the order
+    in which and as soon as they complete.
+
+    This differs from PEP 3148; the proper way to use this is:
+
+        for f in as_completed(fs):
+            result = yield from f  # The 'yield from' may raise.
+            # Use result.
+
+    If a timeout is specified, the 'yield from' will raise
+    TimeoutError when the timeout occurs before all Futures are done.
+
+    Note: The futures 'f' are not necessarily members of fs.
+    """
+    if isinstance(fs, futures.Future) or coroutines.iscoroutine(fs):
+        raise TypeError("expect a list of futures, not %s" % type(fs).__name__)
+    loop = loop if loop is not None else events.get_event_loop()
+    todo = {ensure_future(f, loop=loop) for f in set(fs)}
+    from .queues import Queue  # Import here to avoid circular import problem.
+    done = Queue(loop=loop)
+    timeout_handle = None
+
+    def _on_timeout():
+        for f in todo:
+            f.remove_done_callback(_on_completion)
+            done.put_nowait(None)  # Queue a dummy value for _wait_for_one().
+        todo.clear()  # Can't do todo.remove(f) in the loop.
+
+    def _on_completion(f):
+        if not todo:
+            return  # _on_timeout() was here first.
+        todo.remove(f)
+        done.put_nowait(f)
+        if not todo and timeout_handle is not None:
+            timeout_handle.cancel()
+
+    @coroutine
+    def _wait_for_one():
+        f = yield from done.get()
+        if f is None:
+            # Dummy value from _on_timeout().
+            raise futures.TimeoutError
+        return f.result()  # May raise f.exception().
+
+    for f in todo:
+        f.add_done_callback(_on_completion)
+    if todo and timeout is not None:
+        timeout_handle = loop.call_later(timeout, _on_timeout)
+    for _ in range(len(todo)):
+        yield _wait_for_one()
+
+
+@coroutine
+def sleep(delay, result=None, *, loop=None):
+    """Coroutine that completes after a given time (in seconds)."""
+    future = futures.Future(loop=loop)
+    h = future._loop.call_later(delay,
+                                future._set_result_unless_cancelled, result)
+    try:
+        return (yield from future)
+    finally:
+        h.cancel()
+
+
+def async(coro_or_future, *, loop=None):
+    """Wrap a coroutine in a future.
+
+    If the argument is a Future, it is returned directly.
+
+    This function is deprecated in 3.5. Use asyncio.ensure_future() instead.
+    """
+
+    warnings.warn("asyncio.async() function is deprecated, use ensure_future()",
+                  DeprecationWarning)
+
+    return ensure_future(coro_or_future, loop=loop)
+
+
+def ensure_future(coro_or_future, *, loop=None):
+    """Wrap a coroutine in a future.
+
+    If the argument is a Future, it is returned directly.
+    """
+    if isinstance(coro_or_future, futures.Future):
+        if loop is not None and loop is not coro_or_future._loop:
+            raise ValueError('loop argument must agree with Future')
+        return coro_or_future
+    elif coroutines.iscoroutine(coro_or_future):
+        if loop is None:
+            loop = events.get_event_loop()
+        task = loop.create_task(coro_or_future)
+        if task._source_traceback:
+            del task._source_traceback[-1]
+        return task
+    else:
+        raise TypeError('A Future or coroutine is required')
+
+
+class _GatheringFuture(futures.Future):
+    """Helper for gather().
+
+    This overrides cancel() to cancel all the children and act more
+    like Task.cancel(), which doesn't immediately mark itself as
+    cancelled.
+    """
+
+    def __init__(self, children, *, loop=None):
+        super().__init__(loop=loop)
+        self._children = children
+
+    def cancel(self):
+        if self.done():
+            return False
+        for child in self._children:
+            child.cancel()
+        return True
+
+
+def gather(*coros_or_futures, loop=None, return_exceptions=False):
+    """Return a future aggregating results from the given coroutines
+    or futures.
+
+    All futures must share the same event loop.  If all the tasks are
+    done successfully, the returned future's result is the list of
+    results (in the order of the original sequence, not necessarily
+    the order of results arrival).  If *return_exceptions* is True,
+    exceptions in the tasks are treated the same as successful
+    results, and gathered in the result list; otherwise, the first
+    raised exception will be immediately propagated to the returned
+    future.
+
+    Cancellation: if the outer Future is cancelled, all children (that
+    have not completed yet) are also cancelled.  If any child is
+    cancelled, this is treated as if it raised CancelledError --
+    the outer Future is *not* cancelled in this case.  (This is to
+    prevent the cancellation of one child to cause other children to
+    be cancelled.)
+    """
+    if not coros_or_futures:
+        outer = futures.Future(loop=loop)
+        outer.set_result([])
+        return outer
+
+    arg_to_fut = {}
+    for arg in set(coros_or_futures):
+        if not isinstance(arg, futures.Future):
+            fut = ensure_future(arg, loop=loop)
+            if loop is None:
+                loop = fut._loop
+            # The caller cannot control this future, the "destroy pending task"
+            # warning should not be emitted.
+            fut._log_destroy_pending = False
+        else:
+            fut = arg
+            if loop is None:
+                loop = fut._loop
+            elif fut._loop is not loop:
+                raise ValueError("futures are tied to different event loops")
+        arg_to_fut[arg] = fut
+
+    children = [arg_to_fut[arg] for arg in coros_or_futures]
+    nchildren = len(children)
+    outer = _GatheringFuture(children, loop=loop)
+    nfinished = 0
+    results = [None] * nchildren
+
+    def _done_callback(i, fut):
+        nonlocal nfinished
+        if outer.done():
+            if not fut.cancelled():
+                # Mark exception retrieved.
+                fut.exception()
+            return
+
+        if fut.cancelled():
+            res = futures.CancelledError()
+            if not return_exceptions:
+                outer.set_exception(res)
+                return
+        elif fut._exception is not None:
+            res = fut.exception()  # Mark exception retrieved.
+            if not return_exceptions:
+                outer.set_exception(res)
+                return
+        else:
+            res = fut._result
+        results[i] = res
+        nfinished += 1
+        if nfinished == nchildren:
+            outer.set_result(results)
+
+    for i, fut in enumerate(children):
+        fut.add_done_callback(functools.partial(_done_callback, i))
+    return outer
+
+
+def shield(arg, *, loop=None):
+    """Wait for a future, shielding it from cancellation.
+
+    The statement
+
+        res = yield from shield(something())
+
+    is exactly equivalent to the statement
+
+        res = yield from something()
+
+    *except* that if the coroutine containing it is cancelled, the
+    task running in something() is not cancelled.  From the POV of
+    something(), the cancellation did not happen.  But its caller is
+    still cancelled, so the yield-from expression still raises
+    CancelledError.  Note: If something() is cancelled by other means
+    this will still cancel shield().
+
+    If you want to completely ignore cancellation (not recommended)
+    you can combine shield() with a try/except clause, as follows:
+
+        try:
+            res = yield from shield(something())
+        except CancelledError:
+            res = None
+    """
+    inner = ensure_future(arg, loop=loop)
+    if inner.done():
+        # Shortcut.
+        return inner
+    loop = inner._loop
+    outer = futures.Future(loop=loop)
+
+    def _done_callback(inner):
+        if outer.cancelled():
+            if not inner.cancelled():
+                # Mark inner's result as retrieved.
+                inner.exception()
+            return
+
+        if inner.cancelled():
+            outer.cancel()
+        else:
+            exc = inner.exception()
+            if exc is not None:
+                outer.set_exception(exc)
+            else:
+                outer.set_result(inner.result())
+
+    inner.add_done_callback(_done_callback)
+    return outer
diff --git a/trollius/test_support.py b/trollius/test_support.py
new file mode 100644
index 0000000..0fadfad
--- /dev/null
+++ b/trollius/test_support.py
@@ -0,0 +1,308 @@
+# Subset of test.support from CPython 3.5, just what we need to run asyncio
+# test suite. The code is copied from CPython 3.5 to not depend on the test
+# module because it is rarely installed.
+
+# Ignore symbol TEST_HOME_DIR: test_events works without it
+
+import functools
+import gc
+import os
+import platform
+import re
+import socket
+import subprocess
+import sys
+import time
+
+
+# A constant likely larger than the underlying OS pipe buffer size, to
+# make writes blocking.
+# Windows limit seems to be around 512 B, and many Unix kernels have a
+# 64 KiB pipe buffer size or 16 * PAGE_SIZE: take a few megs to be sure.
+# (see issue #17835 for a discussion of this number).
+PIPE_MAX_SIZE = 4 * 1024 * 1024 + 1
+
+def strip_python_stderr(stderr):
+    """Strip the stderr of a Python process from potential debug output
+    emitted by the interpreter.
+
+    This will typically be run on the result of the communicate() method
+    of a subprocess.Popen object.
+    """
+    stderr = re.sub(br"\[\d+ refs, \d+ blocks\]\r?\n?", b"", stderr).strip()
+    return stderr
+
+
+# Executing the interpreter in a subprocess
+def _assert_python(expected_success, *args, **env_vars):
+    if '__isolated' in env_vars:
+        isolated = env_vars.pop('__isolated')
+    else:
+        isolated = not env_vars
+    cmd_line = [sys.executable, '-X', 'faulthandler']
+    if isolated and sys.version_info >= (3, 4):
+        # isolated mode: ignore Python environment variables, ignore user
+        # site-packages, and don't add the current directory to sys.path
+        cmd_line.append('-I')
+    elif not env_vars:
+        # ignore Python environment variables
+        cmd_line.append('-E')
+    # Need to preserve the original environment, for in-place testing of
+    # shared library builds.
+    env = os.environ.copy()
+    # But a special flag that can be set to override -- in this case, the
+    # caller is responsible to pass the full environment.
+    if env_vars.pop('__cleanenv', None):
+        env = {}
+    env.update(env_vars)
+    cmd_line.extend(args)
+    p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                         env=env)
+    try:
+        out, err = p.communicate()
+    finally:
+        subprocess._cleanup()
+        p.stdout.close()
+        p.stderr.close()
+    rc = p.returncode
+    err = strip_python_stderr(err)
+    if (rc and expected_success) or (not rc and not expected_success):
+        raise AssertionError(
+            "Process return code is %d, "
+            "stderr follows:\n%s" % (rc, err.decode('ascii', 'ignore')))
+    return rc, out, err
+
+
+def assert_python_ok(*args, **env_vars):
+    """
+    Assert that running the interpreter with `args` and optional environment
+    variables `env_vars` succeeds (rc == 0) and return a (return code, stdout,
+    stderr) tuple.
+
+    If the __cleanenv keyword is set, env_vars is used a fresh environment.
+
+    Python is started in isolated mode (command line option -I),
+    except if the __isolated keyword is set to False.
+    """
+    return _assert_python(True, *args, **env_vars)
+
+
+is_jython = sys.platform.startswith('java')
+
+def gc_collect():
+    """Force as many objects as possible to be collected.
+
+    In non-CPython implementations of Python, this is needed because timely
+    deallocation is not guaranteed by the garbage collector.  (Even in CPython
+    this can be the case in case of reference cycles.)  This means that __del__
+    methods may be called later than expected and weakrefs may remain alive for
+    longer than expected.  This function tries its best to force all garbage
+    objects to disappear.
+    """
+    gc.collect()
+    if is_jython:
+        time.sleep(0.1)
+    gc.collect()
+    gc.collect()
+
+
+HOST = "127.0.0.1"
+HOSTv6 = "::1"
+
+
+def _is_ipv6_enabled():
+    """Check whether IPv6 is enabled on this host."""
+    if socket.has_ipv6:
+        sock = None
+        try:
+            sock = socket.socket(socket.AF_INET6, socket.SOCK_STREAM)
+            sock.bind((HOSTv6, 0))
+            return True
+        except OSError:
+            pass
+        finally:
+            if sock:
+                sock.close()
+    return False
+
+IPV6_ENABLED = _is_ipv6_enabled()
+
+
+def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM):
+    """Returns an unused port that should be suitable for binding.  This is
+    achieved by creating a temporary socket with the same family and type as
+    the 'sock' parameter (default is AF_INET, SOCK_STREAM), and binding it to
+    the specified host address (defaults to 0.0.0.0) with the port set to 0,
+    eliciting an unused ephemeral port from the OS.  The temporary socket is
+    then closed and deleted, and the ephemeral port is returned.
+
+    Either this method or bind_port() should be used for any tests where a
+    server socket needs to be bound to a particular port for the duration of
+    the test.  Which one to use depends on whether the calling code is creating
+    a python socket, or if an unused port needs to be provided in a constructor
+    or passed to an external program (i.e. the -accept argument to openssl's
+    s_server mode).  Always prefer bind_port() over find_unused_port() where
+    possible.  Hard coded ports should *NEVER* be used.  As soon as a server
+    socket is bound to a hard coded port, the ability to run multiple instances
+    of the test simultaneously on the same host is compromised, which makes the
+    test a ticking time bomb in a buildbot environment. On Unix buildbots, this
+    may simply manifest as a failed test, which can be recovered from without
+    intervention in most cases, but on Windows, the entire python process can
+    completely and utterly wedge, requiring someone to log in to the buildbot
+    and manually kill the affected process.
+
+    (This is easy to reproduce on Windows, unfortunately, and can be traced to
+    the SO_REUSEADDR socket option having different semantics on Windows versus
+    Unix/Linux.  On Unix, you can't have two AF_INET SOCK_STREAM sockets bind,
+    listen and then accept connections on identical host/ports.  An EADDRINUSE
+    OSError will be raised at some point (depending on the platform and
+    the order bind and listen were called on each socket).
+
+    However, on Windows, if SO_REUSEADDR is set on the sockets, no EADDRINUSE
+    will ever be raised when attempting to bind two identical host/ports. When
+    accept() is called on each socket, the second caller's process will steal
+    the port from the first caller, leaving them both in an awkwardly wedged
+    state where they'll no longer respond to any signals or graceful kills, and
+    must be forcibly killed via OpenProcess()/TerminateProcess().
+
+    The solution on Windows is to use the SO_EXCLUSIVEADDRUSE socket option
+    instead of SO_REUSEADDR, which effectively affords the same semantics as
+    SO_REUSEADDR on Unix.  Given the propensity of Unix developers in the Open
+    Source world compared to Windows ones, this is a common mistake.  A quick
+    look over OpenSSL's 0.9.8g source shows that they use SO_REUSEADDR when
+    openssl.exe is called with the 's_server' option, for example. See
+    http://bugs.python.org/issue2550 for more info.  The following site also
+    has a very thorough description about the implications of both REUSEADDR
+    and EXCLUSIVEADDRUSE on Windows:
+    http://msdn2.microsoft.com/en-us/library/ms740621(VS.85).aspx)
+
+    XXX: although this approach is a vast improvement on previous attempts to
+    elicit unused ports, it rests heavily on the assumption that the ephemeral
+    port returned to us by the OS won't immediately be dished back out to some
+    other process when we close and delete our temporary socket but before our
+    calling code has a chance to bind the returned port.  We can deal with this
+    issue if/when we come across it.
+    """
+
+    tempsock = socket.socket(family, socktype)
+    port = bind_port(tempsock)
+    tempsock.close()
+    del tempsock
+    return port
+
+def bind_port(sock, host=HOST):
+    """Bind the socket to a free port and return the port number.  Relies on
+    ephemeral ports in order to ensure we are using an unbound port.  This is
+    important as many tests may be running simultaneously, especially in a
+    buildbot environment.  This method raises an exception if the sock.family
+    is AF_INET and sock.type is SOCK_STREAM, *and* the socket has SO_REUSEADDR
+    or SO_REUSEPORT set on it.  Tests should *never* set these socket options
+    for TCP/IP sockets.  The only case for setting these options is testing
+    multicasting via multiple UDP sockets.
+
+    Additionally, if the SO_EXCLUSIVEADDRUSE socket option is available (i.e.
+    on Windows), it will be set on the socket.  This will prevent anyone else
+    from bind()'ing to our host/port for the duration of the test.
+    """
+
+    if sock.family == socket.AF_INET and sock.type == socket.SOCK_STREAM:
+        if hasattr(socket, 'SO_REUSEADDR'):
+            if sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR) == 1:
+                raise TestFailed("tests should never set the SO_REUSEADDR "
+                                 "socket option on TCP/IP sockets!")
+        if hasattr(socket, 'SO_REUSEPORT'):
+            try:
+                reuse = sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT)
+                if reuse == 1:
+                    raise TestFailed("tests should never set the SO_REUSEPORT "
+                                     "socket option on TCP/IP sockets!")
+            except OSError:
+                # Python's socket module was compiled using modern headers
+                # thus defining SO_REUSEPORT but this process is running
+                # under an older kernel that does not support SO_REUSEPORT.
+                pass
+        if hasattr(socket, 'SO_EXCLUSIVEADDRUSE'):
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)
+
+    sock.bind((host, 0))
+    port = sock.getsockname()[1]
+    return port
+
+def requires_mac_ver(*min_version):
+    """Decorator raising SkipTest if the OS is Mac OS X and the OS X
+    version if less than min_version.
+
+    For example, @requires_mac_ver(10, 5) raises SkipTest if the OS X version
+    is lesser than 10.5.
+    """
+    def decorator(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kw):
+            if sys.platform == 'darwin':
+                version_txt = platform.mac_ver()[0]
+                try:
+                    version = tuple(map(int, version_txt.split('.')))
+                except ValueError:
+                    pass
+                else:
+                    if version < min_version:
+                        min_version_txt = '.'.join(map(str, min_version))
+                        raise unittest.SkipTest(
+                            "Mac OS X %s or higher required, not %s"
+                            % (min_version_txt, version_txt))
+            return func(*args, **kw)
+        wrapper.min_version = min_version
+        return wrapper
+    return decorator
+
+def _requires_unix_version(sysname, min_version):
+    """Decorator raising SkipTest if the OS is `sysname` and the version is
+    less than `min_version`.
+
+    For example, @_requires_unix_version('FreeBSD', (7, 2)) raises SkipTest if
+    the FreeBSD version is less than 7.2.
+    """
+    def decorator(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kw):
+            if platform.system() == sysname:
+                version_txt = platform.release().split('-', 1)[0]
+                try:
+                    version = tuple(map(int, version_txt.split('.')))
+                except ValueError:
+                    pass
+                else:
+                    if version < min_version:
+                        min_version_txt = '.'.join(map(str, min_version))
+                        raise unittest.SkipTest(
+                            "%s version %s or higher required, not %s"
+                            % (sysname, min_version_txt, version_txt))
+            return func(*args, **kw)
+        wrapper.min_version = min_version
+        return wrapper
+    return decorator
+
+def requires_freebsd_version(*min_version):
+    """Decorator raising SkipTest if the OS is FreeBSD and the FreeBSD version
+    is less than `min_version`.
+
+    For example, @requires_freebsd_version(7, 2) raises SkipTest if the FreeBSD
+    version is less than 7.2.
+    """
+    return _requires_unix_version('FreeBSD', min_version)
+
+# Use test.support if available
+try:
+    from test.support import *
+except ImportError:
+    pass
+
+# Use test.script_helper if available
+try:
+    from test.support.script_helper import assert_python_ok
+except ImportError:
+    try:
+        from test.script_helper import assert_python_ok
+    except ImportError:
+        pass
diff --git a/trollius/test_utils.py b/trollius/test_utils.py
new file mode 100644
index 0000000..8cee95b
--- /dev/null
+++ b/trollius/test_utils.py
@@ -0,0 +1,446 @@
+"""Utilities shared by tests."""
+
+import collections
+import contextlib
+import io
+import logging
+import os
+import re
+import socket
+import socketserver
+import sys
+import tempfile
+import threading
+import time
+import unittest
+from unittest import mock
+
+from http.server import HTTPServer
+from wsgiref.simple_server import WSGIRequestHandler, WSGIServer
+
+try:
+    import ssl
+except ImportError:  # pragma: no cover
+    ssl = None
+
+from . import base_events
+from . import events
+from . import futures
+from . import selectors
+from . import tasks
+from .coroutines import coroutine
+from .log import logger
+
+
+if sys.platform == 'win32':  # pragma: no cover
+    from .windows_utils import socketpair
+else:
+    from socket import socketpair  # pragma: no cover
+
+
+def dummy_ssl_context():
+    if ssl is None:
+        return None
+    else:
+        return ssl.SSLContext(ssl.PROTOCOL_SSLv23)
+
+
+def run_briefly(loop):
+    @coroutine
+    def once():
+        pass
+    gen = once()
+    t = loop.create_task(gen)
+    # Don't log a warning if the task is not done after run_until_complete().
+    # It occurs if the loop is stopped or if a task raises a BaseException.
+    t._log_destroy_pending = False
+    try:
+        loop.run_until_complete(t)
+    finally:
+        gen.close()
+
+
+def run_until(loop, pred, timeout=30):
+    deadline = time.time() + timeout
+    while not pred():
+        if timeout is not None:
+            timeout = deadline - time.time()
+            if timeout <= 0:
+                raise futures.TimeoutError()
+        loop.run_until_complete(tasks.sleep(0.001, loop=loop))
+
+
+def run_once(loop):
+    """loop.stop() schedules _raise_stop_error()
+    and run_forever() runs until _raise_stop_error() callback.
+    this wont work if test waits for some IO events, because
+    _raise_stop_error() runs before any of io events callbacks.
+    """
+    loop.stop()
+    loop.run_forever()
+
+
+class SilentWSGIRequestHandler(WSGIRequestHandler):
+
+    def get_stderr(self):
+        return io.StringIO()
+
+    def log_message(self, format, *args):
+        pass
+
+
+class SilentWSGIServer(WSGIServer):
+
+    request_timeout = 2
+
+    def get_request(self):
+        request, client_addr = super().get_request()
+        request.settimeout(self.request_timeout)
+        return request, client_addr
+
+    def handle_error(self, request, client_address):
+        pass
+
+
+class SSLWSGIServerMixin:
+
+    def finish_request(self, request, client_address):
+        # The relative location of our test directory (which
+        # contains the ssl key and certificate files) differs
+        # between the stdlib and stand-alone asyncio.
+        # Prefer our own if we can find it.
+        here = os.path.join(os.path.dirname(__file__), '..', 'tests')
+        if not os.path.isdir(here):
+            here = os.path.join(os.path.dirname(os.__file__),
+                                'test', 'test_asyncio')
+        keyfile = os.path.join(here, 'ssl_key.pem')
+        certfile = os.path.join(here, 'ssl_cert.pem')
+        ssock = ssl.wrap_socket(request,
+                                keyfile=keyfile,
+                                certfile=certfile,
+                                server_side=True)
+        try:
+            self.RequestHandlerClass(ssock, client_address, self)
+            ssock.close()
+        except OSError:
+            # maybe socket has been closed by peer
+            pass
+
+
+class SSLWSGIServer(SSLWSGIServerMixin, SilentWSGIServer):
+    pass
+
+
+def _run_test_server(*, address, use_ssl=False, server_cls, server_ssl_cls):
+
+    def app(environ, start_response):
+        status = '200 OK'
+        headers = [('Content-type', 'text/plain')]
+        start_response(status, headers)
+        return [b'Test message']
+
+    # Run the test WSGI server in a separate thread in order not to
+    # interfere with event handling in the main thread
+    server_class = server_ssl_cls if use_ssl else server_cls
+    httpd = server_class(address, SilentWSGIRequestHandler)
+    httpd.set_app(app)
+    httpd.address = httpd.server_address
+    server_thread = threading.Thread(
+        target=lambda: httpd.serve_forever(poll_interval=0.05))
+    server_thread.start()
+    try:
+        yield httpd
+    finally:
+        httpd.shutdown()
+        httpd.server_close()
+        server_thread.join()
+
+
+if hasattr(socket, 'AF_UNIX'):
+
+    class UnixHTTPServer(socketserver.UnixStreamServer, HTTPServer):
+
+        def server_bind(self):
+            socketserver.UnixStreamServer.server_bind(self)
+            self.server_name = '127.0.0.1'
+            self.server_port = 80
+
+
+    class UnixWSGIServer(UnixHTTPServer, WSGIServer):
+
+        request_timeout = 2
+
+        def server_bind(self):
+            UnixHTTPServer.server_bind(self)
+            self.setup_environ()
+
+        def get_request(self):
+            request, client_addr = super().get_request()
+            request.settimeout(self.request_timeout)
+            # Code in the stdlib expects that get_request
+            # will return a socket and a tuple (host, port).
+            # However, this isn't true for UNIX sockets,
+            # as the second return value will be a path;
+            # hence we return some fake data sufficient
+            # to get the tests going
+            return request, ('127.0.0.1', '')
+
+
+    class SilentUnixWSGIServer(UnixWSGIServer):
+
+        def handle_error(self, request, client_address):
+            pass
+
+
+    class UnixSSLWSGIServer(SSLWSGIServerMixin, SilentUnixWSGIServer):
+        pass
+
+
+    def gen_unix_socket_path():
+        with tempfile.NamedTemporaryFile() as file:
+            return file.name
+
+
+    @contextlib.contextmanager
+    def unix_socket_path():
+        path = gen_unix_socket_path()
+        try:
+            yield path
+        finally:
+            try:
+                os.unlink(path)
+            except OSError:
+                pass
+
+
+    @contextlib.contextmanager
+    def run_test_unix_server(*, use_ssl=False):
+        with unix_socket_path() as path:
+            yield from _run_test_server(address=path, use_ssl=use_ssl,
+                                        server_cls=SilentUnixWSGIServer,
+                                        server_ssl_cls=UnixSSLWSGIServer)
+
+
+@contextlib.contextmanager
+def run_test_server(*, host='127.0.0.1', port=0, use_ssl=False):
+    yield from _run_test_server(address=(host, port), use_ssl=use_ssl,
+                                server_cls=SilentWSGIServer,
+                                server_ssl_cls=SSLWSGIServer)
+
+
+def make_test_protocol(base):
+    dct = {}
+    for name in dir(base):
+        if name.startswith('__') and name.endswith('__'):
+            # skip magic names
+            continue
+        dct[name] = MockCallback(return_value=None)
+    return type('TestProtocol', (base,) + base.__bases__, dct)()
+
+
+class TestSelector(selectors.BaseSelector):
+
+    def __init__(self):
+        self.keys = {}
+
+    def register(self, fileobj, events, data=None):
+        key = selectors.SelectorKey(fileobj, 0, events, data)
+        self.keys[fileobj] = key
+        return key
+
+    def unregister(self, fileobj):
+        return self.keys.pop(fileobj)
+
+    def select(self, timeout):
+        return []
+
+    def get_map(self):
+        return self.keys
+
+
+class TestLoop(base_events.BaseEventLoop):
+    """Loop for unittests.
+
+    It manages self time directly.
+    If something scheduled to be executed later then
+    on next loop iteration after all ready handlers done
+    generator passed to __init__ is calling.
+
+    Generator should be like this:
+
+        def gen():
+            ...
+            when = yield ...
+            ... = yield time_advance
+
+    Value returned by yield is absolute time of next scheduled handler.
+    Value passed to yield is time advance to move loop's time forward.
+    """
+
+    def __init__(self, gen=None):
+        super().__init__()
+
+        if gen is None:
+            def gen():
+                yield
+            self._check_on_close = False
+        else:
+            self._check_on_close = True
+
+        self._gen = gen()
+        next(self._gen)
+        self._time = 0
+        self._clock_resolution = 1e-9
+        self._timers = []
+        self._selector = TestSelector()
+
+        self.readers = {}
+        self.writers = {}
+        self.reset_counters()
+
+    def time(self):
+        return self._time
+
+    def advance_time(self, advance):
+        """Move test time forward."""
+        if advance:
+            self._time += advance
+
+    def close(self):
+        super().close()
+        if self._check_on_close:
+            try:
+                self._gen.send(0)
+            except StopIteration:
+                pass
+            else:  # pragma: no cover
+                raise AssertionError("Time generator is not finished")
+
+    def add_reader(self, fd, callback, *args):
+        self.readers[fd] = events.Handle(callback, args, self)
+
+    def remove_reader(self, fd):
+        self.remove_reader_count[fd] += 1
+        if fd in self.readers:
+            del self.readers[fd]
+            return True
+        else:
+            return False
+
+    def assert_reader(self, fd, callback, *args):
+        assert fd in self.readers, 'fd {} is not registered'.format(fd)
+        handle = self.readers[fd]
+        assert handle._callback == callback, '{!r} != {!r}'.format(
+            handle._callback, callback)
+        assert handle._args == args, '{!r} != {!r}'.format(
+            handle._args, args)
+
+    def add_writer(self, fd, callback, *args):
+        self.writers[fd] = events.Handle(callback, args, self)
+
+    def remove_writer(self, fd):
+        self.remove_writer_count[fd] += 1
+        if fd in self.writers:
+            del self.writers[fd]
+            return True
+        else:
+            return False
+
+    def assert_writer(self, fd, callback, *args):
+        assert fd in self.writers, 'fd {} is not registered'.format(fd)
+        handle = self.writers[fd]
+        assert handle._callback == callback, '{!r} != {!r}'.format(
+            handle._callback, callback)
+        assert handle._args == args, '{!r} != {!r}'.format(
+            handle._args, args)
+
+    def reset_counters(self):
+        self.remove_reader_count = collections.defaultdict(int)
+        self.remove_writer_count = collections.defaultdict(int)
+
+    def _run_once(self):
+        super()._run_once()
+        for when in self._timers:
+            advance = self._gen.send(when)
+            self.advance_time(advance)
+        self._timers = []
+
+    def call_at(self, when, callback, *args):
+        self._timers.append(when)
+        return super().call_at(when, callback, *args)
+
+    def _process_events(self, event_list):
+        return
+
+    def _write_to_self(self):
+        pass
+
+
+def MockCallback(**kwargs):
+    return mock.Mock(spec=['__call__'], **kwargs)
+
+
+class MockPattern(str):
+    """A regex based str with a fuzzy __eq__.
+
+    Use this helper with 'mock.assert_called_with', or anywhere
+    where a regex comparison between strings is needed.
+
+    For instance:
+       mock_call.assert_called_with(MockPattern('spam.*ham'))
+    """
+    def __eq__(self, other):
+        return bool(re.search(str(self), other, re.S))
+
+
+def get_function_source(func):
+    source = events._get_function_source(func)
+    if source is None:
+        raise ValueError("unable to get the source of %r" % (func,))
+    return source
+
+
+class TestCase(unittest.TestCase):
+    def set_event_loop(self, loop, *, cleanup=True):
+        assert loop is not None
+        # ensure that the event loop is passed explicitly in asyncio
+        events.set_event_loop(None)
+        if cleanup:
+            self.addCleanup(loop.close)
+
+    def new_test_loop(self, gen=None):
+        loop = TestLoop(gen)
+        self.set_event_loop(loop)
+        return loop
+
+    def tearDown(self):
+        events.set_event_loop(None)
+
+        # Detect CPython bug #23353: ensure that yield/yield-from is not used
+        # in an except block of a generator
+        self.assertEqual(sys.exc_info(), (None, None, None))
+
+
+@contextlib.contextmanager
+def disable_logger():
+    """Context manager to disable asyncio logger.
+
+    For example, it can be used to ignore warnings in debug mode.
+    """
+    old_level = logger.level
+    try:
+        logger.setLevel(logging.CRITICAL+1)
+        yield
+    finally:
+        logger.setLevel(old_level)
+
+def mock_nonblocking_socket():
+    """Create a mock of a non-blocking socket."""
+    sock = mock.Mock(socket.socket)
+    sock.gettimeout.return_value = 0.0
+    return sock
+
+
+def force_legacy_ssl_support():
+    return mock.patch('asyncio.sslproto._is_sslproto_available',
+                      return_value=False)
diff --git a/trollius/transports.py b/trollius/transports.py
new file mode 100644
index 0000000..22df3c7
--- /dev/null
+++ b/trollius/transports.py
@@ -0,0 +1,300 @@
+"""Abstract Transport class."""
+
+import sys
+
+_PY34 = sys.version_info >= (3, 4)
+
+__all__ = ['BaseTransport', 'ReadTransport', 'WriteTransport',
+           'Transport', 'DatagramTransport', 'SubprocessTransport',
+           ]
+
+
+class BaseTransport:
+    """Base class for transports."""
+
+    def __init__(self, extra=None):
+        if extra is None:
+            extra = {}
+        self._extra = extra
+
+    def get_extra_info(self, name, default=None):
+        """Get optional transport information."""
+        return self._extra.get(name, default)
+
+    def close(self):
+        """Close the transport.
+
+        Buffered data will be flushed asynchronously.  No more data
+        will be received.  After all buffered data is flushed, the
+        protocol's connection_lost() method will (eventually) called
+        with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class ReadTransport(BaseTransport):
+    """Interface for read-only transports."""
+
+    def pause_reading(self):
+        """Pause the receiving end.
+
+        No data will be passed to the protocol's data_received()
+        method until resume_reading() is called.
+        """
+        raise NotImplementedError
+
+    def resume_reading(self):
+        """Resume the receiving end.
+
+        Data received will once again be passed to the protocol's
+        data_received() method.
+        """
+        raise NotImplementedError
+
+
+class WriteTransport(BaseTransport):
+    """Interface for write-only transports."""
+
+    def set_write_buffer_limits(self, high=None, low=None):
+        """Set the high- and low-water limits for write flow control.
+
+        These two values control when to call the protocol's
+        pause_writing() and resume_writing() methods.  If specified,
+        the low-water limit must be less than or equal to the
+        high-water limit.  Neither value can be negative.
+
+        The defaults are implementation-specific.  If only the
+        high-water limit is given, the low-water limit defaults to a
+        implementation-specific value less than or equal to the
+        high-water limit.  Setting high to zero forces low to zero as
+        well, and causes pause_writing() to be called whenever the
+        buffer becomes non-empty.  Setting low to zero causes
+        resume_writing() to be called only once the buffer is empty.
+        Use of zero for either limit is generally sub-optimal as it
+        reduces opportunities for doing I/O and computation
+        concurrently.
+        """
+        raise NotImplementedError
+
+    def get_write_buffer_size(self):
+        """Return the current size of the write buffer."""
+        raise NotImplementedError
+
+    def write(self, data):
+        """Write some data bytes to the transport.
+
+        This does not block; it buffers the data and arranges for it
+        to be sent out asynchronously.
+        """
+        raise NotImplementedError
+
+    def writelines(self, list_of_data):
+        """Write a list (or any iterable) of data bytes to the transport.
+
+        The default implementation concatenates the arguments and
+        calls write() on the result.
+        """
+        if not _PY34:
+            # In Python 3.3, bytes.join() doesn't handle memoryview.
+            list_of_data = (
+                bytes(data) if isinstance(data, memoryview) else data
+                for data in list_of_data)
+        self.write(b''.join(list_of_data))
+
+    def write_eof(self):
+        """Close the write end after flushing buffered data.
+
+        (This is like typing ^D into a UNIX program reading from stdin.)
+
+        Data may still be received.
+        """
+        raise NotImplementedError
+
+    def can_write_eof(self):
+        """Return True if this transport supports write_eof(), False if not."""
+        raise NotImplementedError
+
+    def abort(self):
+        """Close the transport immediately.
+
+        Buffered data will be lost.  No more data will be received.
+        The protocol's connection_lost() method will (eventually) be
+        called with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class Transport(ReadTransport, WriteTransport):
+    """Interface representing a bidirectional transport.
+
+    There may be several implementations, but typically, the user does
+    not implement new transports; rather, the platform provides some
+    useful transports that are implemented using the platform's best
+    practices.
+
+    The user never instantiates a transport directly; they call a
+    utility function, passing it a protocol factory and other
+    information necessary to create the transport and protocol.  (E.g.
+    EventLoop.create_connection() or EventLoop.create_server().)
+
+    The utility function will asynchronously create a transport and a
+    protocol and hook them up by calling the protocol's
+    connection_made() method, passing it the transport.
+
+    The implementation here raises NotImplemented for every method
+    except writelines(), which calls write() in a loop.
+    """
+
+
+class DatagramTransport(BaseTransport):
+    """Interface for datagram (UDP) transports."""
+
+    def sendto(self, data, addr=None):
+        """Send data to the transport.
+
+        This does not block; it buffers the data and arranges for it
+        to be sent out asynchronously.
+        addr is target socket address.
+        If addr is None use target address pointed on transport creation.
+        """
+        raise NotImplementedError
+
+    def abort(self):
+        """Close the transport immediately.
+
+        Buffered data will be lost.  No more data will be received.
+        The protocol's connection_lost() method will (eventually) be
+        called with None as its argument.
+        """
+        raise NotImplementedError
+
+
+class SubprocessTransport(BaseTransport):
+
+    def get_pid(self):
+        """Get subprocess id."""
+        raise NotImplementedError
+
+    def get_returncode(self):
+        """Get subprocess returncode.
+
+        See also
+        http://docs.python.org/3/library/subprocess#subprocess.Popen.returncode
+        """
+        raise NotImplementedError
+
+    def get_pipe_transport(self, fd):
+        """Get transport for pipe with number fd."""
+        raise NotImplementedError
+
+    def send_signal(self, signal):
+        """Send signal to subprocess.
+
+        See also:
+        docs.python.org/3/library/subprocess#subprocess.Popen.send_signal
+        """
+        raise NotImplementedError
+
+    def terminate(self):
+        """Stop the subprocess.
+
+        Alias for close() method.
+
+        On Posix OSs the method sends SIGTERM to the subprocess.
+        On Windows the Win32 API function TerminateProcess()
+         is called to stop the subprocess.
+
+        See also:
+        http://docs.python.org/3/library/subprocess#subprocess.Popen.terminate
+        """
+        raise NotImplementedError
+
+    def kill(self):
+        """Kill the subprocess.
+
+        On Posix OSs the function sends SIGKILL to the subprocess.
+        On Windows kill() is an alias for terminate().
+
+        See also:
+        http://docs.python.org/3/library/subprocess#subprocess.Popen.kill
+        """
+        raise NotImplementedError
+
+
+class _FlowControlMixin(Transport):
+    """All the logic for (write) flow control in a mix-in base class.
+
+    The subclass must implement get_write_buffer_size().  It must call
+    _maybe_pause_protocol() whenever the write buffer size increases,
+    and _maybe_resume_protocol() whenever it decreases.  It may also
+    override set_write_buffer_limits() (e.g. to specify different
+    defaults).
+
+    The subclass constructor must call super().__init__(extra).  This
+    will call set_write_buffer_limits().
+
+    The user may call set_write_buffer_limits() and
+    get_write_buffer_size(), and their protocol's pause_writing() and
+    resume_writing() may be called.
+    """
+
+    def __init__(self, extra=None, loop=None):
+        super().__init__(extra)
+        assert loop is not None
+        self._loop = loop
+        self._protocol_paused = False
+        self._set_write_buffer_limits()
+
+    def _maybe_pause_protocol(self):
+        size = self.get_write_buffer_size()
+        if size <= self._high_water:
+            return
+        if not self._protocol_paused:
+            self._protocol_paused = True
+            try:
+                self._protocol.pause_writing()
+            except Exception as exc:
+                self._loop.call_exception_handler({
+                    'message': 'protocol.pause_writing() failed',
+                    'exception': exc,
+                    'transport': self,
+                    'protocol': self._protocol,
+                })
+
+    def _maybe_resume_protocol(self):
+        if (self._protocol_paused and
+            self.get_write_buffer_size() <= self._low_water):
+            self._protocol_paused = False
+            try:
+                self._protocol.resume_writing()
+            except Exception as exc:
+                self._loop.call_exception_handler({
+                    'message': 'protocol.resume_writing() failed',
+                    'exception': exc,
+                    'transport': self,
+                    'protocol': self._protocol,
+                })
+
+    def get_write_buffer_limits(self):
+        return (self._low_water, self._high_water)
+
+    def _set_write_buffer_limits(self, high=None, low=None):
+        if high is None:
+            if low is None:
+                high = 64*1024
+            else:
+                high = 4*low
+        if low is None:
+            low = high // 4
+        if not high >= low >= 0:
+            raise ValueError('high (%r) must be >= low (%r) must be >= 0' %
+                             (high, low))
+        self._high_water = high
+        self._low_water = low
+
+    def set_write_buffer_limits(self, high=None, low=None):
+        self._set_write_buffer_limits(high=high, low=low)
+        self._maybe_pause_protocol()
+
+    def get_write_buffer_size(self):
+        raise NotImplementedError
diff --git a/trollius/unix_events.py b/trollius/unix_events.py
new file mode 100644
index 0000000..75e7c9c
--- /dev/null
+++ b/trollius/unix_events.py
@@ -0,0 +1,998 @@
+"""Selector event loop for Unix with signal handling."""
+
+import errno
+import os
+import signal
+import socket
+import stat
+import subprocess
+import sys
+import threading
+import warnings
+
+
+from . import base_events
+from . import base_subprocess
+from . import constants
+from . import coroutines
+from . import events
+from . import futures
+from . import selector_events
+from . import selectors
+from . import transports
+from .coroutines import coroutine
+from .log import logger
+
+
+__all__ = ['SelectorEventLoop',
+           'AbstractChildWatcher', 'SafeChildWatcher',
+           'FastChildWatcher', 'DefaultEventLoopPolicy',
+           ]
+
+if sys.platform == 'win32':  # pragma: no cover
+    raise ImportError('Signals are not really supported on Windows')
+
+
+def _sighandler_noop(signum, frame):
+    """Dummy signal handler."""
+    pass
+
+
+class _UnixSelectorEventLoop(selector_events.BaseSelectorEventLoop):
+    """Unix event loop.
+
+    Adds signal handling and UNIX Domain Socket support to SelectorEventLoop.
+    """
+
+    def __init__(self, selector=None):
+        super().__init__(selector)
+        self._signal_handlers = {}
+
+    def _socketpair(self):
+        return socket.socketpair()
+
+    def close(self):
+        super().close()
+        for sig in list(self._signal_handlers):
+            self.remove_signal_handler(sig)
+
+    def _process_self_data(self, data):
+        for signum in data:
+            if not signum:
+                # ignore null bytes written by _write_to_self()
+                continue
+            self._handle_signal(signum)
+
+    def add_signal_handler(self, sig, callback, *args):
+        """Add a handler for a signal.  UNIX only.
+
+        Raise ValueError if the signal number is invalid or uncatchable.
+        Raise RuntimeError if there is a problem setting up the handler.
+        """
+        if (coroutines.iscoroutine(callback)
+        or coroutines.iscoroutinefunction(callback)):
+            raise TypeError("coroutines cannot be used "
+                            "with add_signal_handler()")
+        self._check_signal(sig)
+        self._check_closed()
+        try:
+            # set_wakeup_fd() raises ValueError if this is not the
+            # main thread.  By calling it early we ensure that an
+            # event loop running in another thread cannot add a signal
+            # handler.
+            signal.set_wakeup_fd(self._csock.fileno())
+        except (ValueError, OSError) as exc:
+            raise RuntimeError(str(exc))
+
+        handle = events.Handle(callback, args, self)
+        self._signal_handlers[sig] = handle
+
+        try:
+            # Register a dummy signal handler to ask Python to write the signal
+            # number in the wakup file descriptor. _process_self_data() will
+            # read signal numbers from this file descriptor to handle signals.
+            signal.signal(sig, _sighandler_noop)
+
+            # Set SA_RESTART to limit EINTR occurrences.
+            signal.siginterrupt(sig, False)
+        except OSError as exc:
+            del self._signal_handlers[sig]
+            if not self._signal_handlers:
+                try:
+                    signal.set_wakeup_fd(-1)
+                except (ValueError, OSError) as nexc:
+                    logger.info('set_wakeup_fd(-1) failed: %s', nexc)
+
+            if exc.errno == errno.EINVAL:
+                raise RuntimeError('sig {} cannot be caught'.format(sig))
+            else:
+                raise
+
+    def _handle_signal(self, sig):
+        """Internal helper that is the actual signal handler."""
+        handle = self._signal_handlers.get(sig)
+        if handle is None:
+            return  # Assume it's some race condition.
+        if handle._cancelled:
+            self.remove_signal_handler(sig)  # Remove it properly.
+        else:
+            self._add_callback_signalsafe(handle)
+
+    def remove_signal_handler(self, sig):
+        """Remove a handler for a signal.  UNIX only.
+
+        Return True if a signal handler was removed, False if not.
+        """
+        self._check_signal(sig)
+        try:
+            del self._signal_handlers[sig]
+        except KeyError:
+            return False
+
+        if sig == signal.SIGINT:
+            handler = signal.default_int_handler
+        else:
+            handler = signal.SIG_DFL
+
+        try:
+            signal.signal(sig, handler)
+        except OSError as exc:
+            if exc.errno == errno.EINVAL:
+                raise RuntimeError('sig {} cannot be caught'.format(sig))
+            else:
+                raise
+
+        if not self._signal_handlers:
+            try:
+                signal.set_wakeup_fd(-1)
+            except (ValueError, OSError) as exc:
+                logger.info('set_wakeup_fd(-1) failed: %s', exc)
+
+        return True
+
+    def _check_signal(self, sig):
+        """Internal helper to validate a signal.
+
+        Raise ValueError if the signal number is invalid or uncatchable.
+        Raise RuntimeError if there is a problem setting up the handler.
+        """
+        if not isinstance(sig, int):
+            raise TypeError('sig must be an int, not {!r}'.format(sig))
+
+        if not (1 <= sig < signal.NSIG):
+            raise ValueError(
+                'sig {} out of range(1, {})'.format(sig, signal.NSIG))
+
+    def _make_read_pipe_transport(self, pipe, protocol, waiter=None,
+                                  extra=None):
+        return _UnixReadPipeTransport(self, pipe, protocol, waiter, extra)
+
+    def _make_write_pipe_transport(self, pipe, protocol, waiter=None,
+                                   extra=None):
+        return _UnixWritePipeTransport(self, pipe, protocol, waiter, extra)
+
+    @coroutine
+    def _make_subprocess_transport(self, protocol, args, shell,
+                                   stdin, stdout, stderr, bufsize,
+                                   extra=None, **kwargs):
+        with events.get_child_watcher() as watcher:
+            waiter = futures.Future(loop=self)
+            transp = _UnixSubprocessTransport(self, protocol, args, shell,
+                                              stdin, stdout, stderr, bufsize,
+                                              waiter=waiter, extra=extra,
+                                              **kwargs)
+
+            watcher.add_child_handler(transp.get_pid(),
+                                      self._child_watcher_callback, transp)
+            try:
+                yield from waiter
+            except Exception as exc:
+                # Workaround CPython bug #23353: using yield/yield-from in an
+                # except block of a generator doesn't clear properly
+                # sys.exc_info()
+                err = exc
+            else:
+                err = None
+
+            if err is not None:
+                transp.close()
+                yield from transp._wait()
+                raise err
+
+        return transp
+
+    def _child_watcher_callback(self, pid, returncode, transp):
+        self.call_soon_threadsafe(transp._process_exited, returncode)
+
+    @coroutine
+    def create_unix_connection(self, protocol_factory, path, *,
+                               ssl=None, sock=None,
+                               server_hostname=None):
+        assert server_hostname is None or isinstance(server_hostname, str)
+        if ssl:
+            if server_hostname is None:
+                raise ValueError(
+                    'you have to pass server_hostname when using ssl')
+        else:
+            if server_hostname is not None:
+                raise ValueError('server_hostname is only meaningful with ssl')
+
+        if path is not None:
+            if sock is not None:
+                raise ValueError(
+                    'path and sock can not be specified at the same time')
+
+            sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0)
+            try:
+                sock.setblocking(False)
+                yield from self.sock_connect(sock, path)
+            except:
+                sock.close()
+                raise
+
+        else:
+            if sock is None:
+                raise ValueError('no path and sock were specified')
+            sock.setblocking(False)
+
+        transport, protocol = yield from self._create_connection_transport(
+            sock, protocol_factory, ssl, server_hostname)
+        return transport, protocol
+
+    @coroutine
+    def create_unix_server(self, protocol_factory, path=None, *,
+                           sock=None, backlog=100, ssl=None):
+        if isinstance(ssl, bool):
+            raise TypeError('ssl argument must be an SSLContext or None')
+
+        if path is not None:
+            if sock is not None:
+                raise ValueError(
+                    'path and sock can not be specified at the same time')
+
+            sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+
+            try:
+                sock.bind(path)
+            except OSError as exc:
+                sock.close()
+                if exc.errno == errno.EADDRINUSE:
+                    # Let's improve the error message by adding
+                    # with what exact address it occurs.
+                    msg = 'Address {!r} is already in use'.format(path)
+                    raise OSError(errno.EADDRINUSE, msg) from None
+                else:
+                    raise
+            except:
+                sock.close()
+                raise
+        else:
+            if sock is None:
+                raise ValueError(
+                    'path was not specified, and no sock specified')
+
+            if sock.family != socket.AF_UNIX:
+                raise ValueError(
+                    'A UNIX Domain Socket was expected, got {!r}'.format(sock))
+
+        server = base_events.Server(self, [sock])
+        sock.listen(backlog)
+        sock.setblocking(False)
+        self._start_serving(protocol_factory, sock, ssl, server)
+        return server
+
+
+if hasattr(os, 'set_blocking'):
+    def _set_nonblocking(fd):
+        os.set_blocking(fd, False)
+else:
+    import fcntl
+
+    def _set_nonblocking(fd):
+        flags = fcntl.fcntl(fd, fcntl.F_GETFL)
+        flags = flags | os.O_NONBLOCK
+        fcntl.fcntl(fd, fcntl.F_SETFL, flags)
+
+
+class _UnixReadPipeTransport(transports.ReadTransport):
+
+    max_size = 256 * 1024  # max bytes we read in one event loop iteration
+
+    def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
+        super().__init__(extra)
+        self._extra['pipe'] = pipe
+        self._loop = loop
+        self._pipe = pipe
+        self._fileno = pipe.fileno()
+        mode = os.fstat(self._fileno).st_mode
+        if not (stat.S_ISFIFO(mode) or
+                stat.S_ISSOCK(mode) or
+                stat.S_ISCHR(mode)):
+            raise ValueError("Pipe transport is for pipes/sockets only.")
+        _set_nonblocking(self._fileno)
+        self._protocol = protocol
+        self._closing = False
+        self._loop.call_soon(self._protocol.connection_made, self)
+        # only start reading when connection_made() has been called
+        self._loop.call_soon(self._loop.add_reader,
+                             self._fileno, self._read_ready)
+        if waiter is not None:
+            # only wake up the waiter when connection_made() has been called
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self._pipe is None:
+            info.append('closed')
+        elif self._closing:
+            info.append('closing')
+        info.append('fd=%s' % self._fileno)
+        if self._pipe is not None:
+            polling = selector_events._test_selector_event(
+                          self._loop._selector,
+                          self._fileno, selectors.EVENT_READ)
+            if polling:
+                info.append('polling')
+            else:
+                info.append('idle')
+        else:
+            info.append('closed')
+        return '<%s>' % ' '.join(info)
+
+    def _read_ready(self):
+        try:
+            data = os.read(self._fileno, self.max_size)
+        except (BlockingIOError, InterruptedError):
+            pass
+        except OSError as exc:
+            self._fatal_error(exc, 'Fatal read error on pipe transport')
+        else:
+            if data:
+                self._protocol.data_received(data)
+            else:
+                if self._loop.get_debug():
+                    logger.info("%r was closed by peer", self)
+                self._closing = True
+                self._loop.remove_reader(self._fileno)
+                self._loop.call_soon(self._protocol.eof_received)
+                self._loop.call_soon(self._call_connection_lost, None)
+
+    def pause_reading(self):
+        self._loop.remove_reader(self._fileno)
+
+    def resume_reading(self):
+        self._loop.add_reader(self._fileno, self._read_ready)
+
+    def close(self):
+        if not self._closing:
+            self._close(None)
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if self._pipe is not None:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self._pipe.close()
+
+    def _fatal_error(self, exc, message='Fatal error on pipe transport'):
+        # should be called by exception handler only
+        if (isinstance(exc, OSError) and exc.errno == errno.EIO):
+            if self._loop.get_debug():
+                logger.debug("%r: %s", self, message, exc_info=True)
+        else:
+            self._loop.call_exception_handler({
+                'message': message,
+                'exception': exc,
+                'transport': self,
+                'protocol': self._protocol,
+            })
+        self._close(exc)
+
+    def _close(self, exc):
+        self._closing = True
+        self._loop.remove_reader(self._fileno)
+        self._loop.call_soon(self._call_connection_lost, exc)
+
+    def _call_connection_lost(self, exc):
+        try:
+            self._protocol.connection_lost(exc)
+        finally:
+            self._pipe.close()
+            self._pipe = None
+            self._protocol = None
+            self._loop = None
+
+
+class _UnixWritePipeTransport(transports._FlowControlMixin,
+                              transports.WriteTransport):
+
+    def __init__(self, loop, pipe, protocol, waiter=None, extra=None):
+        super().__init__(extra, loop)
+        self._extra['pipe'] = pipe
+        self._pipe = pipe
+        self._fileno = pipe.fileno()
+        mode = os.fstat(self._fileno).st_mode
+        is_socket = stat.S_ISSOCK(mode)
+        if not (is_socket or
+                stat.S_ISFIFO(mode) or
+                stat.S_ISCHR(mode)):
+            raise ValueError("Pipe transport is only for "
+                             "pipes, sockets and character devices")
+        _set_nonblocking(self._fileno)
+        self._protocol = protocol
+        self._buffer = []
+        self._conn_lost = 0
+        self._closing = False  # Set when close() or write_eof() called.
+
+        self._loop.call_soon(self._protocol.connection_made, self)
+
+        # On AIX, the reader trick (to be notified when the read end of the
+        # socket is closed) only works for sockets. On other platforms it
+        # works for pipes and sockets. (Exception: OS X 10.4?  Issue #19294.)
+        if is_socket or not sys.platform.startswith("aix"):
+            # only start reading when connection_made() has been called
+            self._loop.call_soon(self._loop.add_reader,
+                                 self._fileno, self._read_ready)
+
+        if waiter is not None:
+            # only wake up the waiter when connection_made() has been called
+            self._loop.call_soon(waiter._set_result_unless_cancelled, None)
+
+    def __repr__(self):
+        info = [self.__class__.__name__]
+        if self._pipe is None:
+            info.append('closed')
+        elif self._closing:
+            info.append('closing')
+        info.append('fd=%s' % self._fileno)
+        if self._pipe is not None:
+            polling = selector_events._test_selector_event(
+                          self._loop._selector,
+                          self._fileno, selectors.EVENT_WRITE)
+            if polling:
+                info.append('polling')
+            else:
+                info.append('idle')
+
+            bufsize = self.get_write_buffer_size()
+            info.append('bufsize=%s' % bufsize)
+        else:
+            info.append('closed')
+        return '<%s>' % ' '.join(info)
+
+    def get_write_buffer_size(self):
+        return sum(len(data) for data in self._buffer)
+
+    def _read_ready(self):
+        # Pipe was closed by peer.
+        if self._loop.get_debug():
+            logger.info("%r was closed by peer", self)
+        if self._buffer:
+            self._close(BrokenPipeError())
+        else:
+            self._close()
+
+    def write(self, data):
+        assert isinstance(data, (bytes, bytearray, memoryview)), repr(data)
+        if isinstance(data, bytearray):
+            data = memoryview(data)
+        if not data:
+            return
+
+        if self._conn_lost or self._closing:
+            if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+                logger.warning('pipe closed by peer or '
+                               'os.write(pipe, data) raised exception.')
+            self._conn_lost += 1
+            return
+
+        if not self._buffer:
+            # Attempt to send it right away first.
+            try:
+                n = os.write(self._fileno, data)
+            except (BlockingIOError, InterruptedError):
+                n = 0
+            except Exception as exc:
+                self._conn_lost += 1
+                self._fatal_error(exc, 'Fatal write error on pipe transport')
+                return
+            if n == len(data):
+                return
+            elif n > 0:
+                data = data[n:]
+            self._loop.add_writer(self._fileno, self._write_ready)
+
+        self._buffer.append(data)
+        self._maybe_pause_protocol()
+
+    def _write_ready(self):
+        data = b''.join(self._buffer)
+        assert data, 'Data should not be empty'
+
+        self._buffer.clear()
+        try:
+            n = os.write(self._fileno, data)
+        except (BlockingIOError, InterruptedError):
+            self._buffer.append(data)
+        except Exception as exc:
+            self._conn_lost += 1
+            # Remove writer here, _fatal_error() doesn't it
+            # because _buffer is empty.
+            self._loop.remove_writer(self._fileno)
+            self._fatal_error(exc, 'Fatal write error on pipe transport')
+        else:
+            if n == len(data):
+                self._loop.remove_writer(self._fileno)
+                self._maybe_resume_protocol()  # May append to buffer.
+                if not self._buffer and self._closing:
+                    self._loop.remove_reader(self._fileno)
+                    self._call_connection_lost(None)
+                return
+            elif n > 0:
+                data = data[n:]
+
+            self._buffer.append(data)  # Try again later.
+
+    def can_write_eof(self):
+        return True
+
+    def write_eof(self):
+        if self._closing:
+            return
+        assert self._pipe
+        self._closing = True
+        if not self._buffer:
+            self._loop.remove_reader(self._fileno)
+            self._loop.call_soon(self._call_connection_lost, None)
+
+    def close(self):
+        if self._pipe is not None and not self._closing:
+            # write_eof is all what we needed to close the write pipe
+            self.write_eof()
+
+    # On Python 3.3 and older, objects with a destructor part of a reference
+    # cycle are never destroyed. It's not more the case on Python 3.4 thanks
+    # to the PEP 442.
+    if sys.version_info >= (3, 4):
+        def __del__(self):
+            if self._pipe is not None:
+                warnings.warn("unclosed transport %r" % self, ResourceWarning)
+                self._pipe.close()
+
+    def abort(self):
+        self._close(None)
+
+    def _fatal_error(self, exc, message='Fatal error on pipe transport'):
+        # should be called by exception handler only
+        if isinstance(exc, (BrokenPipeError, ConnectionResetError)):
+            if self._loop.get_debug():
+                logger.debug("%r: %s", self, message, exc_info=True)
+        else:
+            self._loop.call_exception_handler({
+                'message': message,
+                'exception': exc,
+                'transport': self,
+                'protocol': self._protocol,
+            })
+        self._close(exc)
+
+    def _close(self, exc=None):
+        self._closing = True
+        if self._buffer:
+            self._loop.remove_writer(self._fileno)
+        self._buffer.clear()
+        self._loop.remove_reader(self._fileno)
+        self._loop.call_soon(self._call_connection_lost, exc)
+
+    def _call_connection_lost(self, exc):
+        try:
+            self._protocol.connection_lost(exc)
+        finally:
+            self._pipe.close()
+            self._pipe = None
+            self._protocol = None
+            self._loop = None
+
+
+if hasattr(os, 'set_inheritable'):
+    # Python 3.4 and newer
+    _set_inheritable = os.set_inheritable
+else:
+    import fcntl
+
+    def _set_inheritable(fd, inheritable):
+        cloexec_flag = getattr(fcntl, 'FD_CLOEXEC', 1)
+
+        old = fcntl.fcntl(fd, fcntl.F_GETFD)
+        if not inheritable:
+            fcntl.fcntl(fd, fcntl.F_SETFD, old | cloexec_flag)
+        else:
+            fcntl.fcntl(fd, fcntl.F_SETFD, old & ~cloexec_flag)
+
+
+class _UnixSubprocessTransport(base_subprocess.BaseSubprocessTransport):
+
+    def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs):
+        stdin_w = None
+        if stdin == subprocess.PIPE:
+            # Use a socket pair for stdin, since not all platforms
+            # support selecting read events on the write end of a
+            # socket (which we use in order to detect closing of the
+            # other end).  Notably this is needed on AIX, and works
+            # just fine on other platforms.
+            stdin, stdin_w = self._loop._socketpair()
+
+            # Mark the write end of the stdin pipe as non-inheritable,
+            # needed by close_fds=False on Python 3.3 and older
+            # (Python 3.4 implements the PEP 446, socketpair returns
+            # non-inheritable sockets)
+            _set_inheritable(stdin_w.fileno(), False)
+        self._proc = subprocess.Popen(
+            args, shell=shell, stdin=stdin, stdout=stdout, stderr=stderr,
+            universal_newlines=False, bufsize=bufsize, **kwargs)
+        if stdin_w is not None:
+            stdin.close()
+            self._proc.stdin = open(stdin_w.detach(), 'wb', buffering=bufsize)
+
+
+class AbstractChildWatcher:
+    """Abstract base class for monitoring child processes.
+
+    Objects derived from this class monitor a collection of subprocesses and
+    report their termination or interruption by a signal.
+
+    New callbacks are registered with .add_child_handler(). Starting a new
+    process must be done within a 'with' block to allow the watcher to suspend
+    its activity until the new process if fully registered (this is needed to
+    prevent a race condition in some implementations).
+
+    Example:
+        with watcher:
+            proc = subprocess.Popen("sleep 1")
+            watcher.add_child_handler(proc.pid, callback)
+
+    Notes:
+        Implementations of this class must be thread-safe.
+
+        Since child watcher objects may catch the SIGCHLD signal and call
+        waitpid(-1), there should be only one active object per process.
+    """
+
+    def add_child_handler(self, pid, callback, *args):
+        """Register a new child handler.
+
+        Arrange for callback(pid, returncode, *args) to be called when
+        process 'pid' terminates. Specifying another callback for the same
+        process replaces the previous handler.
+
+        Note: callback() must be thread-safe.
+        """
+        raise NotImplementedError()
+
+    def remove_child_handler(self, pid):
+        """Removes the handler for process 'pid'.
+
+        The function returns True if the handler was successfully removed,
+        False if there was nothing to remove."""
+
+        raise NotImplementedError()
+
+    def attach_loop(self, loop):
+        """Attach the watcher to an event loop.
+
+        If the watcher was previously attached to an event loop, then it is
+        first detached before attaching to the new loop.
+
+        Note: loop may be None.
+        """
+        raise NotImplementedError()
+
+    def close(self):
+        """Close the watcher.
+
+        This must be called to make sure that any underlying resource is freed.
+        """
+        raise NotImplementedError()
+
+    def __enter__(self):
+        """Enter the watcher's context and allow starting new processes
+
+        This function must return self"""
+        raise NotImplementedError()
+
+    def __exit__(self, a, b, c):
+        """Exit the watcher's context"""
+        raise NotImplementedError()
+
+
+class BaseChildWatcher(AbstractChildWatcher):
+
+    def __init__(self):
+        self._loop = None
+
+    def close(self):
+        self.attach_loop(None)
+
+    def _do_waitpid(self, expected_pid):
+        raise NotImplementedError()
+
+    def _do_waitpid_all(self):
+        raise NotImplementedError()
+
+    def attach_loop(self, loop):
+        assert loop is None or isinstance(loop, events.AbstractEventLoop)
+
+        if self._loop is not None:
+            self._loop.remove_signal_handler(signal.SIGCHLD)
+
+        self._loop = loop
+        if loop is not None:
+            loop.add_signal_handler(signal.SIGCHLD, self._sig_chld)
+
+            # Prevent a race condition in case a child terminated
+            # during the switch.
+            self._do_waitpid_all()
+
+    def _sig_chld(self):
+        try:
+            self._do_waitpid_all()
+        except Exception as exc:
+            # self._loop should always be available here
+            # as '_sig_chld' is added as a signal handler
+            # in 'attach_loop'
+            self._loop.call_exception_handler({
+                'message': 'Unknown exception in SIGCHLD handler',
+                'exception': exc,
+            })
+
+    def _compute_returncode(self, status):
+        if os.WIFSIGNALED(status):
+            # The child process died because of a signal.
+            return -os.WTERMSIG(status)
+        elif os.WIFEXITED(status):
+            # The child process exited (e.g sys.exit()).
+            return os.WEXITSTATUS(status)
+        else:
+            # The child exited, but we don't understand its status.
+            # This shouldn't happen, but if it does, let's just
+            # return that status; perhaps that helps debug it.
+            return status
+
+
+class SafeChildWatcher(BaseChildWatcher):
+    """'Safe' child watcher implementation.
+
+    This implementation avoids disrupting other code spawning processes by
+    polling explicitly each process in the SIGCHLD handler instead of calling
+    os.waitpid(-1).
+
+    This is a safe solution but it has a significant overhead when handling a
+    big number of children (O(n) each time SIGCHLD is raised)
+    """
+
+    def __init__(self):
+        super().__init__()
+        self._callbacks = {}
+
+    def close(self):
+        self._callbacks.clear()
+        super().close()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, a, b, c):
+        pass
+
+    def add_child_handler(self, pid, callback, *args):
+        self._callbacks[pid] = (callback, args)
+
+        # Prevent a race condition in case the child is already terminated.
+        self._do_waitpid(pid)
+
+    def remove_child_handler(self, pid):
+        try:
+            del self._callbacks[pid]
+            return True
+        except KeyError:
+            return False
+
+    def _do_waitpid_all(self):
+
+        for pid in list(self._callbacks):
+            self._do_waitpid(pid)
+
+    def _do_waitpid(self, expected_pid):
+        assert expected_pid > 0
+
+        try:
+            pid, status = os.waitpid(expected_pid, os.WNOHANG)
+        except ChildProcessError:
+            # The child process is already reaped
+            # (may happen if waitpid() is called elsewhere).
+            pid = expected_pid
+            returncode = 255
+            logger.warning(
+                "Unknown child process pid %d, will report returncode 255",
+                pid)
+        else:
+            if pid == 0:
+                # The child process is still alive.
+                return
+
+            returncode = self._compute_returncode(status)
+            if self._loop.get_debug():
+                logger.debug('process %s exited with returncode %s',
+                             expected_pid, returncode)
+
+        try:
+            callback, args = self._callbacks.pop(pid)
+        except KeyError:  # pragma: no cover
+            # May happen if .remove_child_handler() is called
+            # after os.waitpid() returns.
+            if self._loop.get_debug():
+                logger.warning("Child watcher got an unexpected pid: %r",
+                               pid, exc_info=True)
+        else:
+            callback(pid, returncode, *args)
+
+
+class FastChildWatcher(BaseChildWatcher):
+    """'Fast' child watcher implementation.
+
+    This implementation reaps every terminated processes by calling
+    os.waitpid(-1) directly, possibly breaking other code spawning processes
+    and waiting for their termination.
+
+    There is no noticeable overhead when handling a big number of children
+    (O(1) each time a child terminates).
+    """
+    def __init__(self):
+        super().__init__()
+        self._callbacks = {}
+        self._lock = threading.Lock()
+        self._zombies = {}
+        self._forks = 0
+
+    def close(self):
+        self._callbacks.clear()
+        self._zombies.clear()
+        super().close()
+
+    def __enter__(self):
+        with self._lock:
+            self._forks += 1
+
+            return self
+
+    def __exit__(self, a, b, c):
+        with self._lock:
+            self._forks -= 1
+
+            if self._forks or not self._zombies:
+                return
+
+            collateral_victims = str(self._zombies)
+            self._zombies.clear()
+
+        logger.warning(
+            "Caught subprocesses termination from unknown pids: %s",
+            collateral_victims)
+
+    def add_child_handler(self, pid, callback, *args):
+        assert self._forks, "Must use the context manager"
+        with self._lock:
+            try:
+                returncode = self._zombies.pop(pid)
+            except KeyError:
+                # The child is running.
+                self._callbacks[pid] = callback, args
+                return
+
+        # The child is dead already. We can fire the callback.
+        callback(pid, returncode, *args)
+
+    def remove_child_handler(self, pid):
+        try:
+            del self._callbacks[pid]
+            return True
+        except KeyError:
+            return False
+
+    def _do_waitpid_all(self):
+        # Because of signal coalescing, we must keep calling waitpid() as
+        # long as we're able to reap a child.
+        while True:
+            try:
+                pid, status = os.waitpid(-1, os.WNOHANG)
+            except ChildProcessError:
+                # No more child processes exist.
+                return
+            else:
+                if pid == 0:
+                    # A child process is still alive.
+                    return
+
+                returncode = self._compute_returncode(status)
+
+            with self._lock:
+                try:
+                    callback, args = self._callbacks.pop(pid)
+                except KeyError:
+                    # unknown child
+                    if self._forks:
+                        # It may not be registered yet.
+                        self._zombies[pid] = returncode
+                        if self._loop.get_debug():
+                            logger.debug('unknown process %s exited '
+                                         'with returncode %s',
+                                         pid, returncode)
+                        continue
+                    callback = None
+                else:
+                    if self._loop.get_debug():
+                        logger.debug('process %s exited with returncode %s',
+                                     pid, returncode)
+
+            if callback is None:
+                logger.warning(
+                    "Caught subprocess termination from unknown pid: "
+                    "%d -> %d", pid, returncode)
+            else:
+                callback(pid, returncode, *args)
+
+
+class _UnixDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
+    """UNIX event loop policy with a watcher for child processes."""
+    _loop_factory = _UnixSelectorEventLoop
+
+    def __init__(self):
+        super().__init__()
+        self._watcher = None
+
+    def _init_watcher(self):
+        with events._lock:
+            if self._watcher is None:  # pragma: no branch
+                self._watcher = SafeChildWatcher()
+                if isinstance(threading.current_thread(),
+                              threading._MainThread):
+                    self._watcher.attach_loop(self._local._loop)
+
+    def set_event_loop(self, loop):
+        """Set the event loop.
+
+        As a side effect, if a child watcher was set before, then calling
+        .set_event_loop() from the main thread will call .attach_loop(loop) on
+        the child watcher.
+        """
+
+        super().set_event_loop(loop)
+
+        if self._watcher is not None and \
+            isinstance(threading.current_thread(), threading._MainThread):
+            self._watcher.attach_loop(loop)
+
+    def get_child_watcher(self):
+        """Get the watcher for child processes.
+
+        If not yet set, a SafeChildWatcher object is automatically created.
+        """
+        if self._watcher is None:
+            self._init_watcher()
+
+        return self._watcher
+
+    def set_child_watcher(self, watcher):
+        """Set the watcher for child processes."""
+
+        assert watcher is None or isinstance(watcher, AbstractChildWatcher)
+
+        if self._watcher is not None:
+            self._watcher.close()
+
+        self._watcher = watcher
+
+SelectorEventLoop = _UnixSelectorEventLoop
+DefaultEventLoopPolicy = _UnixDefaultEventLoopPolicy
diff --git a/trollius/windows_events.py b/trollius/windows_events.py
new file mode 100644
index 0000000..922594f
--- /dev/null
+++ b/trollius/windows_events.py
@@ -0,0 +1,774 @@
+"""Selector and proactor event loops for Windows."""
+
+import _winapi
+import errno
+import math
+import socket
+import struct
+import weakref
+
+from . import events
+from . import base_subprocess
+from . import futures
+from . import proactor_events
+from . import selector_events
+from . import tasks
+from . import windows_utils
+from . import _overlapped
+from .coroutines import coroutine
+from .log import logger
+
+
+__all__ = ['SelectorEventLoop', 'ProactorEventLoop', 'IocpProactor',
+           'DefaultEventLoopPolicy',
+           ]
+
+
+NULL = 0
+INFINITE = 0xffffffff
+ERROR_CONNECTION_REFUSED = 1225
+ERROR_CONNECTION_ABORTED = 1236
+
+# Initial delay in seconds for connect_pipe() before retrying to connect
+CONNECT_PIPE_INIT_DELAY = 0.001
+
+# Maximum delay in seconds for connect_pipe() before retrying to connect
+CONNECT_PIPE_MAX_DELAY = 0.100
+
+
+class _OverlappedFuture(futures.Future):
+    """Subclass of Future which represents an overlapped operation.
+
+    Cancelling it will immediately cancel the overlapped operation.
+    """
+
+    def __init__(self, ov, *, loop=None):
+        super().__init__(loop=loop)
+        if self._source_traceback:
+            del self._source_traceback[-1]
+        self._ov = ov
+
+    def _repr_info(self):
+        info = super()._repr_info()
+        if self._ov is not None:
+            state = 'pending' if self._ov.pending else 'completed'
+            info.insert(1, 'overlapped=<%s, %#x>' % (state, self._ov.address))
+        return info
+
+    def _cancel_overlapped(self):
+        if self._ov is None:
+            return
+        try:
+            self._ov.cancel()
+        except OSError as exc:
+            context = {
+                'message': 'Cancelling an overlapped future failed',
+                'exception': exc,
+                'future': self,
+            }
+            if self._source_traceback:
+                context['source_traceback'] = self._source_traceback
+            self._loop.call_exception_handler(context)
+        self._ov = None
+
+    def cancel(self):
+        self._cancel_overlapped()
+        return super().cancel()
+
+    def set_exception(self, exception):
+        super().set_exception(exception)
+        self._cancel_overlapped()
+
+    def set_result(self, result):
+        super().set_result(result)
+        self._ov = None
+
+
+class _BaseWaitHandleFuture(futures.Future):
+    """Subclass of Future which represents a wait handle."""
+
+    def __init__(self, ov, handle, wait_handle, *, loop=None):
+        super().__init__(loop=loop)
+        if self._source_traceback:
+            del self._source_traceback[-1]
+        # Keep a reference to the Overlapped object to keep it alive until the
+        # wait is unregistered
+        self._ov = ov
+        self._handle = handle
+        self._wait_handle = wait_handle
+
+        # Should we call UnregisterWaitEx() if the wait completes
+        # or is cancelled?
+        self._registered = True
+
+    def _poll(self):
+        # non-blocking wait: use a timeout of 0 millisecond
+        return (_winapi.WaitForSingleObject(self._handle, 0) ==
+                _winapi.WAIT_OBJECT_0)
+
+    def _repr_info(self):
+        info = super()._repr_info()
+        info.append('handle=%#x' % self._handle)
+        if self._handle is not None:
+            state = 'signaled' if self._poll() else 'waiting'
+            info.append(state)
+        if self._wait_handle is not None:
+            info.append('wait_handle=%#x' % self._wait_handle)
+        return info
+
+    def _unregister_wait_cb(self, fut):
+        # The wait was unregistered: it's not safe to destroy the Overlapped
+        # object
+        self._ov = None
+
+    def _unregister_wait(self):
+        if not self._registered:
+            return
+        self._registered = False
+
+        wait_handle = self._wait_handle
+        self._wait_handle = None
+        try:
+            _overlapped.UnregisterWait(wait_handle)
+        except OSError as exc:
+            if exc.winerror != _overlapped.ERROR_IO_PENDING:
+                context = {
+                    'message': 'Failed to unregister the wait handle',
+                    'exception': exc,
+                    'future': self,
+                }
+                if self._source_traceback:
+                    context['source_traceback'] = self._source_traceback
+                self._loop.call_exception_handler(context)
+                return
+            # ERROR_IO_PENDING means that the unregister is pending
+
+        self._unregister_wait_cb(None)
+
+    def cancel(self):
+        self._unregister_wait()
+        return super().cancel()
+
+    def set_exception(self, exception):
+        self._unregister_wait()
+        super().set_exception(exception)
+
+    def set_result(self, result):
+        self._unregister_wait()
+        super().set_result(result)
+
+
+class _WaitCancelFuture(_BaseWaitHandleFuture):
+    """Subclass of Future which represents a wait for the cancellation of a
+    _WaitHandleFuture using an event.
+    """
+
+    def __init__(self, ov, event, wait_handle, *, loop=None):
+        super().__init__(ov, event, wait_handle, loop=loop)
+
+        self._done_callback = None
+
+    def cancel(self):
+        raise RuntimeError("_WaitCancelFuture must not be cancelled")
+
+    def _schedule_callbacks(self):
+        super(_WaitCancelFuture, self)._schedule_callbacks()
+        if self._done_callback is not None:
+            self._done_callback(self)
+
+
+class _WaitHandleFuture(_BaseWaitHandleFuture):
+    def __init__(self, ov, handle, wait_handle, proactor, *, loop=None):
+        super().__init__(ov, handle, wait_handle, loop=loop)
+        self._proactor = proactor
+        self._unregister_proactor = True
+        self._event = _overlapped.CreateEvent(None, True, False, None)
+        self._event_fut = None
+
+    def _unregister_wait_cb(self, fut):
+        if self._event is not None:
+            _winapi.CloseHandle(self._event)
+            self._event = None
+            self._event_fut = None
+
+        # If the wait was cancelled, the wait may never be signalled, so
+        # it's required to unregister it. Otherwise, IocpProactor.close() will
+        # wait forever for an event which will never come.
+        #
+        # If the IocpProactor already received the event, it's safe to call
+        # _unregister() because we kept a reference to the Overlapped object
+        # which is used as an unique key.
+        self._proactor._unregister(self._ov)
+        self._proactor = None
+
+        super()._unregister_wait_cb(fut)
+
+    def _unregister_wait(self):
+        if not self._registered:
+            return
+        self._registered = False
+
+        wait_handle = self._wait_handle
+        self._wait_handle = None
+        try:
+            _overlapped.UnregisterWaitEx(wait_handle, self._event)
+        except OSError as exc:
+            if exc.winerror != _overlapped.ERROR_IO_PENDING:
+                context = {
+                    'message': 'Failed to unregister the wait handle',
+                    'exception': exc,
+                    'future': self,
+                }
+                if self._source_traceback:
+                    context['source_traceback'] = self._source_traceback
+                self._loop.call_exception_handler(context)
+                return
+            # ERROR_IO_PENDING is not an error, the wait was unregistered
+
+        self._event_fut = self._proactor._wait_cancel(self._event,
+                                                      self._unregister_wait_cb)
+
+
+class PipeServer(object):
+    """Class representing a pipe server.
+
+    This is much like a bound, listening socket.
+    """
+    def __init__(self, address):
+        self._address = address
+        self._free_instances = weakref.WeakSet()
+        # initialize the pipe attribute before calling _server_pipe_handle()
+        # because this function can raise an exception and the destructor calls
+        # the close() method
+        self._pipe = None
+        self._accept_pipe_future = None
+        self._pipe = self._server_pipe_handle(True)
+
+    def _get_unconnected_pipe(self):
+        # Create new instance and return previous one.  This ensures
+        # that (until the server is closed) there is always at least
+        # one pipe handle for address.  Therefore if a client attempt
+        # to connect it will not fail with FileNotFoundError.
+        tmp, self._pipe = self._pipe, self._server_pipe_handle(False)
+        return tmp
+
+    def _server_pipe_handle(self, first):
+        # Return a wrapper for a new pipe handle.
+        if self.closed():
+            return None
+        flags = _winapi.PIPE_ACCESS_DUPLEX | _winapi.FILE_FLAG_OVERLAPPED
+        if first:
+            flags |= _winapi.FILE_FLAG_FIRST_PIPE_INSTANCE
+        h = _winapi.CreateNamedPipe(
+            self._address, flags,
+            _winapi.PIPE_TYPE_MESSAGE | _winapi.PIPE_READMODE_MESSAGE |
+            _winapi.PIPE_WAIT,
+            _winapi.PIPE_UNLIMITED_INSTANCES,
+            windows_utils.BUFSIZE, windows_utils.BUFSIZE,
+            _winapi.NMPWAIT_WAIT_FOREVER, _winapi.NULL)
+        pipe = windows_utils.PipeHandle(h)
+        self._free_instances.add(pipe)
+        return pipe
+
+    def closed(self):
+        return (self._address is None)
+
+    def close(self):
+        if self._accept_pipe_future is not None:
+            self._accept_pipe_future.cancel()
+            self._accept_pipe_future = None
+        # Close all instances which have not been connected to by a client.
+        if self._address is not None:
+            for pipe in self._free_instances:
+                pipe.close()
+            self._pipe = None
+            self._address = None
+            self._free_instances.clear()
+
+    __del__ = close
+
+
+class _WindowsSelectorEventLoop(selector_events.BaseSelectorEventLoop):
+    """Windows version of selector event loop."""
+
+    def _socketpair(self):
+        return windows_utils.socketpair()
+
+
+class ProactorEventLoop(proactor_events.BaseProactorEventLoop):
+    """Windows version of proactor event loop using IOCP."""
+
+    def __init__(self, proactor=None):
+        if proactor is None:
+            proactor = IocpProactor()
+        super().__init__(proactor)
+
+    def _socketpair(self):
+        return windows_utils.socketpair()
+
+    @coroutine
+    def create_pipe_connection(self, protocol_factory, address):
+        f = self._proactor.connect_pipe(address)
+        pipe = yield from f
+        protocol = protocol_factory()
+        trans = self._make_duplex_pipe_transport(pipe, protocol,
+                                                 extra={'addr': address})
+        return trans, protocol
+
+    @coroutine
+    def start_serving_pipe(self, protocol_factory, address):
+        server = PipeServer(address)
+
+        def loop_accept_pipe(f=None):
+            pipe = None
+            try:
+                if f:
+                    pipe = f.result()
+                    server._free_instances.discard(pipe)
+
+                    if server.closed():
+                        # A client connected before the server was closed:
+                        # drop the client (close the pipe) and exit
+                        pipe.close()
+                        return
+
+                    protocol = protocol_factory()
+                    self._make_duplex_pipe_transport(
+                        pipe, protocol, extra={'addr': address})
+
+                pipe = server._get_unconnected_pipe()
+                if pipe is None:
+                    return
+
+                f = self._proactor.accept_pipe(pipe)
+            except OSError as exc:
+                if pipe and pipe.fileno() != -1:
+                    self.call_exception_handler({
+                        'message': 'Pipe accept failed',
+                        'exception': exc,
+                        'pipe': pipe,
+                    })
+                    pipe.close()
+                elif self._debug:
+                    logger.warning("Accept pipe failed on pipe %r",
+                                   pipe, exc_info=True)
+            except futures.CancelledError:
+                if pipe:
+                    pipe.close()
+            else:
+                server._accept_pipe_future = f
+                f.add_done_callback(loop_accept_pipe)
+
+        self.call_soon(loop_accept_pipe)
+        return [server]
+
+    @coroutine
+    def _make_subprocess_transport(self, protocol, args, shell,
+                                   stdin, stdout, stderr, bufsize,
+                                   extra=None, **kwargs):
+        waiter = futures.Future(loop=self)
+        transp = _WindowsSubprocessTransport(self, protocol, args, shell,
+                                             stdin, stdout, stderr, bufsize,
+                                             waiter=waiter, extra=extra,
+                                             **kwargs)
+        try:
+            yield from waiter
+        except Exception as exc:
+            # Workaround CPython bug #23353: using yield/yield-from in an
+            # except block of a generator doesn't clear properly sys.exc_info()
+            err = exc
+        else:
+            err = None
+
+        if err is not None:
+            transp.close()
+            yield from transp._wait()
+            raise err
+
+        return transp
+
+
+class IocpProactor:
+    """Proactor implementation using IOCP."""
+
+    def __init__(self, concurrency=0xffffffff):
+        self._loop = None
+        self._results = []
+        self._iocp = _overlapped.CreateIoCompletionPort(
+            _overlapped.INVALID_HANDLE_VALUE, NULL, 0, concurrency)
+        self._cache = {}
+        self._registered = weakref.WeakSet()
+        self._unregistered = []
+        self._stopped_serving = weakref.WeakSet()
+
+    def __repr__(self):
+        return ('<%s overlapped#=%s result#=%s>'
+                % (self.__class__.__name__, len(self._cache),
+                   len(self._results)))
+
+    def set_loop(self, loop):
+        self._loop = loop
+
+    def select(self, timeout=None):
+        if not self._results:
+            self._poll(timeout)
+        tmp = self._results
+        self._results = []
+        return tmp
+
+    def _result(self, value):
+        fut = futures.Future(loop=self._loop)
+        fut.set_result(value)
+        return fut
+
+    def recv(self, conn, nbytes, flags=0):
+        self._register_with_iocp(conn)
+        ov = _overlapped.Overlapped(NULL)
+        try:
+            if isinstance(conn, socket.socket):
+                ov.WSARecv(conn.fileno(), nbytes, flags)
+            else:
+                ov.ReadFile(conn.fileno(), nbytes)
+        except BrokenPipeError:
+            return self._result(b'')
+
+        def finish_recv(trans, key, ov):
+            try:
+                return ov.getresult()
+            except OSError as exc:
+                if exc.winerror == _overlapped.ERROR_NETNAME_DELETED:
+                    raise ConnectionResetError(*exc.args)
+                else:
+                    raise
+
+        return self._register(ov, conn, finish_recv)
+
+    def send(self, conn, buf, flags=0):
+        self._register_with_iocp(conn)
+        ov = _overlapped.Overlapped(NULL)
+        if isinstance(conn, socket.socket):
+            ov.WSASend(conn.fileno(), buf, flags)
+        else:
+            ov.WriteFile(conn.fileno(), buf)
+
+        def finish_send(trans, key, ov):
+            try:
+                return ov.getresult()
+            except OSError as exc:
+                if exc.winerror == _overlapped.ERROR_NETNAME_DELETED:
+                    raise ConnectionResetError(*exc.args)
+                else:
+                    raise
+
+        return self._register(ov, conn, finish_send)
+
+    def accept(self, listener):
+        self._register_with_iocp(listener)
+        conn = self._get_accept_socket(listener.family)
+        ov = _overlapped.Overlapped(NULL)
+        ov.AcceptEx(listener.fileno(), conn.fileno())
+
+        def finish_accept(trans, key, ov):
+            ov.getresult()
+            # Use SO_UPDATE_ACCEPT_CONTEXT so getsockname() etc work.
+            buf = struct.pack('@P', listener.fileno())
+            conn.setsockopt(socket.SOL_SOCKET,
+                            _overlapped.SO_UPDATE_ACCEPT_CONTEXT, buf)
+            conn.settimeout(listener.gettimeout())
+            return conn, conn.getpeername()
+
+        @coroutine
+        def accept_coro(future, conn):
+            # Coroutine closing the accept socket if the future is cancelled
+            try:
+                yield from future
+            except futures.CancelledError:
+                conn.close()
+                raise
+
+        future = self._register(ov, listener, finish_accept)
+        coro = accept_coro(future, conn)
+        tasks.ensure_future(coro, loop=self._loop)
+        return future
+
+    def connect(self, conn, address):
+        self._register_with_iocp(conn)
+        # The socket needs to be locally bound before we call ConnectEx().
+        try:
+            _overlapped.BindLocal(conn.fileno(), conn.family)
+        except OSError as e:
+            if e.winerror != errno.WSAEINVAL:
+                raise
+            # Probably already locally bound; check using getsockname().
+            if conn.getsockname()[1] == 0:
+                raise
+        ov = _overlapped.Overlapped(NULL)
+        ov.ConnectEx(conn.fileno(), address)
+
+        def finish_connect(trans, key, ov):
+            ov.getresult()
+            # Use SO_UPDATE_CONNECT_CONTEXT so getsockname() etc work.
+            conn.setsockopt(socket.SOL_SOCKET,
+                            _overlapped.SO_UPDATE_CONNECT_CONTEXT, 0)
+            return conn
+
+        return self._register(ov, conn, finish_connect)
+
+    def accept_pipe(self, pipe):
+        self._register_with_iocp(pipe)
+        ov = _overlapped.Overlapped(NULL)
+        connected = ov.ConnectNamedPipe(pipe.fileno())
+
+        if connected:
+            # ConnectNamePipe() failed with ERROR_PIPE_CONNECTED which means
+            # that the pipe is connected. There is no need to wait for the
+            # completion of the connection.
+            return self._result(pipe)
+
+        def finish_accept_pipe(trans, key, ov):
+            ov.getresult()
+            return pipe
+
+        return self._register(ov, pipe, finish_accept_pipe)
+
+    @coroutine
+    def connect_pipe(self, address):
+        delay = CONNECT_PIPE_INIT_DELAY
+        while True:
+            # Unfortunately there is no way to do an overlapped connect to a pipe.
+            # Call CreateFile() in a loop until it doesn't fail with
+            # ERROR_PIPE_BUSY
+            try:
+                handle = _overlapped.ConnectPipe(address)
+                break
+            except OSError as exc:
+                if exc.winerror != _overlapped.ERROR_PIPE_BUSY:
+                    raise
+
+            # ConnectPipe() failed with ERROR_PIPE_BUSY: retry later
+            delay = min(delay * 2, CONNECT_PIPE_MAX_DELAY)
+            yield from tasks.sleep(delay, loop=self._loop)
+
+        return windows_utils.PipeHandle(handle)
+
+    def wait_for_handle(self, handle, timeout=None):
+        """Wait for a handle.
+
+        Return a Future object. The result of the future is True if the wait
+        completed, or False if the wait did not complete (on timeout).
+        """
+        return self._wait_for_handle(handle, timeout, False)
+
+    def _wait_cancel(self, event, done_callback):
+        fut = self._wait_for_handle(event, None, True)
+        # add_done_callback() cannot be used because the wait may only complete
+        # in IocpProactor.close(), while the event loop is not running.
+        fut._done_callback = done_callback
+        return fut
+
+    def _wait_for_handle(self, handle, timeout, _is_cancel):
+        if timeout is None:
+            ms = _winapi.INFINITE
+        else:
+            # RegisterWaitForSingleObject() has a resolution of 1 millisecond,
+            # round away from zero to wait *at least* timeout seconds.
+            ms = math.ceil(timeout * 1e3)
+
+        # We only create ov so we can use ov.address as a key for the cache.
+        ov = _overlapped.Overlapped(NULL)
+        wait_handle = _overlapped.RegisterWaitWithQueue(
+            handle, self._iocp, ov.address, ms)
+        if _is_cancel:
+            f = _WaitCancelFuture(ov, handle, wait_handle, loop=self._loop)
+        else:
+            f = _WaitHandleFuture(ov, handle, wait_handle, self,
+                                  loop=self._loop)
+        if f._source_traceback:
+            del f._source_traceback[-1]
+
+        def finish_wait_for_handle(trans, key, ov):
+            # Note that this second wait means that we should only use
+            # this with handles types where a successful wait has no
+            # effect.  So events or processes are all right, but locks
+            # or semaphores are not.  Also note if the handle is
+            # signalled and then quickly reset, then we may return
+            # False even though we have not timed out.
+            return f._poll()
+
+        self._cache[ov.address] = (f, ov, 0, finish_wait_for_handle)
+        return f
+
+    def _register_with_iocp(self, obj):
+        # To get notifications of finished ops on this objects sent to the
+        # completion port, were must register the handle.
+        if obj not in self._registered:
+            self._registered.add(obj)
+            _overlapped.CreateIoCompletionPort(obj.fileno(), self._iocp, 0, 0)
+            # XXX We could also use SetFileCompletionNotificationModes()
+            # to avoid sending notifications to completion port of ops
+            # that succeed immediately.
+
+    def _register(self, ov, obj, callback):
+        # Return a future which will be set with the result of the
+        # operation when it completes.  The future's value is actually
+        # the value returned by callback().
+        f = _OverlappedFuture(ov, loop=self._loop)
+        if f._source_traceback:
+            del f._source_traceback[-1]
+        if not ov.pending:
+            # The operation has completed, so no need to postpone the
+            # work.  We cannot take this short cut if we need the
+            # NumberOfBytes, CompletionKey values returned by
+            # PostQueuedCompletionStatus().
+            try:
+                value = callback(None, None, ov)
+            except OSError as e:
+                f.set_exception(e)
+            else:
+                f.set_result(value)
+            # Even if GetOverlappedResult() was called, we have to wait for the
+            # notification of the completion in GetQueuedCompletionStatus().
+            # Register the overlapped operation to keep a reference to the
+            # OVERLAPPED object, otherwise the memory is freed and Windows may
+            # read uninitialized memory.
+
+        # Register the overlapped operation for later.  Note that
+        # we only store obj to prevent it from being garbage
+        # collected too early.
+        self._cache[ov.address] = (f, ov, obj, callback)
+        return f
+
+    def _unregister(self, ov):
+        """Unregister an overlapped object.
+
+        Call this method when its future has been cancelled. The event can
+        already be signalled (pending in the proactor event queue). It is also
+        safe if the event is never signalled (because it was cancelled).
+        """
+        self._unregistered.append(ov)
+
+    def _get_accept_socket(self, family):
+        s = socket.socket(family)
+        s.settimeout(0)
+        return s
+
+    def _poll(self, timeout=None):
+        if timeout is None:
+            ms = INFINITE
+        elif timeout < 0:
+            raise ValueError("negative timeout")
+        else:
+            # GetQueuedCompletionStatus() has a resolution of 1 millisecond,
+            # round away from zero to wait *at least* timeout seconds.
+            ms = math.ceil(timeout * 1e3)
+            if ms >= INFINITE:
+                raise ValueError("timeout too big")
+
+        while True:
+            status = _overlapped.GetQueuedCompletionStatus(self._iocp, ms)
+            if status is None:
+                break
+            ms = 0
+
+            err, transferred, key, address = status
+            try:
+                f, ov, obj, callback = self._cache.pop(address)
+            except KeyError:
+                if self._loop.get_debug():
+                    self._loop.call_exception_handler({
+                        'message': ('GetQueuedCompletionStatus() returned an '
+                                    'unexpected event'),
+                        'status': ('err=%s transferred=%s key=%#x address=%#x'
+                                   % (err, transferred, key, address)),
+                    })
+
+                # key is either zero, or it is used to return a pipe
+                # handle which should be closed to avoid a leak.
+                if key not in (0, _overlapped.INVALID_HANDLE_VALUE):
+                    _winapi.CloseHandle(key)
+                continue
+
+            if obj in self._stopped_serving:
+                f.cancel()
+            # Don't call the callback if _register() already read the result or
+            # if the overlapped has been cancelled
+            elif not f.done():
+                try:
+                    value = callback(transferred, key, ov)
+                except OSError as e:
+                    f.set_exception(e)
+                    self._results.append(f)
+                else:
+                    f.set_result(value)
+                    self._results.append(f)
+
+        # Remove unregisted futures
+        for ov in self._unregistered:
+            self._cache.pop(ov.address, None)
+        self._unregistered.clear()
+
+    def _stop_serving(self, obj):
+        # obj is a socket or pipe handle.  It will be closed in
+        # BaseProactorEventLoop._stop_serving() which will make any
+        # pending operations fail quickly.
+        self._stopped_serving.add(obj)
+
+    def close(self):
+        # Cancel remaining registered operations.
+        for address, (fut, ov, obj, callback) in list(self._cache.items()):
+            if fut.cancelled():
+                # Nothing to do with cancelled futures
+                pass
+            elif isinstance(fut, _WaitCancelFuture):
+                # _WaitCancelFuture must not be cancelled
+                pass
+            else:
+                try:
+                    fut.cancel()
+                except OSError as exc:
+                    if self._loop is not None:
+                        context = {
+                            'message': 'Cancelling a future failed',
+                            'exception': exc,
+                            'future': fut,
+                        }
+                        if fut._source_traceback:
+                            context['source_traceback'] = fut._source_traceback
+                        self._loop.call_exception_handler(context)
+
+        while self._cache:
+            if not self._poll(1):
+                logger.debug('taking long time to close proactor')
+
+        self._results = []
+        if self._iocp is not None:
+            _winapi.CloseHandle(self._iocp)
+            self._iocp = None
+
+    def __del__(self):
+        self.close()
+
+
+class _WindowsSubprocessTransport(base_subprocess.BaseSubprocessTransport):
+
+    def _start(self, args, shell, stdin, stdout, stderr, bufsize, **kwargs):
+        self._proc = windows_utils.Popen(
+            args, shell=shell, stdin=stdin, stdout=stdout, stderr=stderr,
+            bufsize=bufsize, **kwargs)
+
+        def callback(f):
+            returncode = self._proc.poll()
+            self._process_exited(returncode)
+
+        f = self._loop._proactor.wait_for_handle(int(self._proc._handle))
+        f.add_done_callback(callback)
+
+
+SelectorEventLoop = _WindowsSelectorEventLoop
+
+
+class _WindowsDefaultEventLoopPolicy(events.BaseDefaultEventLoopPolicy):
+    _loop_factory = SelectorEventLoop
+
+
+DefaultEventLoopPolicy = _WindowsDefaultEventLoopPolicy
diff --git a/trollius/windows_utils.py b/trollius/windows_utils.py
new file mode 100644
index 0000000..870cd13
--- /dev/null
+++ b/trollius/windows_utils.py
@@ -0,0 +1,223 @@
+"""
+Various Windows specific bits and pieces
+"""
+
+import sys
+
+if sys.platform != 'win32':  # pragma: no cover
+    raise ImportError('win32 only')
+
+import _winapi
+import itertools
+import msvcrt
+import os
+import socket
+import subprocess
+import tempfile
+import warnings
+
+
+__all__ = ['socketpair', 'pipe', 'Popen', 'PIPE', 'PipeHandle']
+
+
+# Constants/globals
+
+
+BUFSIZE = 8192
+PIPE = subprocess.PIPE
+STDOUT = subprocess.STDOUT
+_mmap_counter = itertools.count()
+
+
+if hasattr(socket, 'socketpair'):
+    # Since Python 3.5, socket.socketpair() is now also available on Windows
+    socketpair = socket.socketpair
+else:
+    # Replacement for socket.socketpair()
+    def socketpair(family=socket.AF_INET, type=socket.SOCK_STREAM, proto=0):
+        """A socket pair usable as a self-pipe, for Windows.
+
+        Origin: https://gist.github.com/4325783, by Geert Jansen.
+        Public domain.
+        """
+        if family == socket.AF_INET:
+            host = '127.0.0.1'
+        elif family == socket.AF_INET6:
+            host = '::1'
+        else:
+            raise ValueError("Only AF_INET and AF_INET6 socket address "
+                             "families are supported")
+        if type != socket.SOCK_STREAM:
+            raise ValueError("Only SOCK_STREAM socket type is supported")
+        if proto != 0:
+            raise ValueError("Only protocol zero is supported")
+
+        # We create a connected TCP socket. Note the trick with setblocking(0)
+        # that prevents us from having to create a thread.
+        lsock = socket.socket(family, type, proto)
+        try:
+            lsock.bind((host, 0))
+            lsock.listen(1)
+            # On IPv6, ignore flow_info and scope_id
+            addr, port = lsock.getsockname()[:2]
+            csock = socket.socket(family, type, proto)
+            try:
+                csock.setblocking(False)
+                try:
+                    csock.connect((addr, port))
+                except (BlockingIOError, InterruptedError):
+                    pass
+                csock.setblocking(True)
+                ssock, _ = lsock.accept()
+            except:
+                csock.close()
+                raise
+        finally:
+            lsock.close()
+        return (ssock, csock)
+
+
+# Replacement for os.pipe() using handles instead of fds
+
+
+def pipe(*, duplex=False, overlapped=(True, True), bufsize=BUFSIZE):
+    """Like os.pipe() but with overlapped support and using handles not fds."""
+    address = tempfile.mktemp(prefix=r'\\.\pipe\python-pipe-%d-%d-' %
+                              (os.getpid(), next(_mmap_counter)))
+
+    if duplex:
+        openmode = _winapi.PIPE_ACCESS_DUPLEX
+        access = _winapi.GENERIC_READ | _winapi.GENERIC_WRITE
+        obsize, ibsize = bufsize, bufsize
+    else:
+        openmode = _winapi.PIPE_ACCESS_INBOUND
+        access = _winapi.GENERIC_WRITE
+        obsize, ibsize = 0, bufsize
+
+    openmode |= _winapi.FILE_FLAG_FIRST_PIPE_INSTANCE
+
+    if overlapped[0]:
+        openmode |= _winapi.FILE_FLAG_OVERLAPPED
+
+    if overlapped[1]:
+        flags_and_attribs = _winapi.FILE_FLAG_OVERLAPPED
+    else:
+        flags_and_attribs = 0
+
+    h1 = h2 = None
+    try:
+        h1 = _winapi.CreateNamedPipe(
+            address, openmode, _winapi.PIPE_WAIT,
+            1, obsize, ibsize, _winapi.NMPWAIT_WAIT_FOREVER, _winapi.NULL)
+
+        h2 = _winapi.CreateFile(
+            address, access, 0, _winapi.NULL, _winapi.OPEN_EXISTING,
+            flags_and_attribs, _winapi.NULL)
+
+        ov = _winapi.ConnectNamedPipe(h1, overlapped=True)
+        ov.GetOverlappedResult(True)
+        return h1, h2
+    except:
+        if h1 is not None:
+            _winapi.CloseHandle(h1)
+        if h2 is not None:
+            _winapi.CloseHandle(h2)
+        raise
+
+
+# Wrapper for a pipe handle
+
+
+class PipeHandle:
+    """Wrapper for an overlapped pipe handle which is vaguely file-object like.
+
+    The IOCP event loop can use these instead of socket objects.
+    """
+    def __init__(self, handle):
+        self._handle = handle
+
+    def __repr__(self):
+        if self._handle is not None:
+            handle = 'handle=%r' % self._handle
+        else:
+            handle = 'closed'
+        return '<%s %s>' % (self.__class__.__name__, handle)
+
+    @property
+    def handle(self):
+        return self._handle
+
+    def fileno(self):
+        if self._handle is None:
+            raise ValueError("I/O operatioon on closed pipe")
+        return self._handle
+
+    def close(self, *, CloseHandle=_winapi.CloseHandle):
+        if self._handle is not None:
+            CloseHandle(self._handle)
+            self._handle = None
+
+    def __del__(self):
+        if self._handle is not None:
+            warnings.warn("unclosed %r" % self, ResourceWarning)
+            self.close()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, t, v, tb):
+        self.close()
+
+
+# Replacement for subprocess.Popen using overlapped pipe handles
+
+
+class Popen(subprocess.Popen):
+    """Replacement for subprocess.Popen using overlapped pipe handles.
+
+    The stdin, stdout, stderr are None or instances of PipeHandle.
+    """
+    def __init__(self, args, stdin=None, stdout=None, stderr=None, **kwds):
+        assert not kwds.get('universal_newlines')
+        assert kwds.get('bufsize', 0) == 0
+        stdin_rfd = stdout_wfd = stderr_wfd = None
+        stdin_wh = stdout_rh = stderr_rh = None
+        if stdin == PIPE:
+            stdin_rh, stdin_wh = pipe(overlapped=(False, True), duplex=True)
+            stdin_rfd = msvcrt.open_osfhandle(stdin_rh, os.O_RDONLY)
+        else:
+            stdin_rfd = stdin
+        if stdout == PIPE:
+            stdout_rh, stdout_wh = pipe(overlapped=(True, False))
+            stdout_wfd = msvcrt.open_osfhandle(stdout_wh, 0)
+        else:
+            stdout_wfd = stdout
+        if stderr == PIPE:
+            stderr_rh, stderr_wh = pipe(overlapped=(True, False))
+            stderr_wfd = msvcrt.open_osfhandle(stderr_wh, 0)
+        elif stderr == STDOUT:
+            stderr_wfd = stdout_wfd
+        else:
+            stderr_wfd = stderr
+        try:
+            super().__init__(args, stdin=stdin_rfd, stdout=stdout_wfd,
+                             stderr=stderr_wfd, **kwds)
+        except:
+            for h in (stdin_wh, stdout_rh, stderr_rh):
+                if h is not None:
+                    _winapi.CloseHandle(h)
+            raise
+        else:
+            if stdin_wh is not None:
+                self.stdin = PipeHandle(stdin_wh)
+            if stdout_rh is not None:
+                self.stdout = PipeHandle(stdout_rh)
+            if stderr_rh is not None:
+                self.stderr = PipeHandle(stderr_rh)
+        finally:
+            if stdin == PIPE:
+                os.close(stdin_rfd)
+            if stdout == PIPE:
+                os.close(stdout_wfd)
+            if stderr == PIPE:
+                os.close(stderr_wfd)