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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
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** General Public License version 3.0 as published by the Free Software
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** packaging of this file. Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
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**
** If you are unsure which license is appropriate for your use, please
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****************************************************************************/
/*!
\example network/threadedfortuneserver
\title Threaded Fortune Server Example
The Threaded Fortune Server example shows how to create a server for a
simple network service that uses threads to handle requests from different
clients. It is intended to be run alongside the Fortune Client example.
\image threadedfortuneserver-example.png
The implementation of this example is similar to that of the
\l{network/fortuneserver}{Fortune Server} example, but here we will
implement a subclass of QTcpServer that starts each connection in a
different thread.
For this we need two classes: FortuneServer, a QTcpServer subclass, and
FortuneThread, which inherits QThread.
\snippet examples/network/threadedfortuneserver/fortuneserver.h 0
FortuneServer inherits QTcpServer and reimplements
QTcpServer::incomingConnection(). We also use it for storing the list of
random fortunes.
\snippet examples/network/threadedfortuneserver/fortuneserver.cpp 0
We use FortuneServer's constructor to simply generate the list of
fortunes.
\snippet examples/network/threadedfortuneserver/fortuneserver.cpp 1
Our implementation of QTcpServer::incomingConnection() creates a
FortuneThread object, passing the incoming socket descriptor and a random
fortune to FortuneThread's constructor. By connecting FortuneThread's
finished() signal to QObject::deleteLater(), we ensure that the thread
gets deleted once it has finished. We can then call QThread::start(),
which starts the thread.
\snippet examples/network/threadedfortuneserver/fortunethread.h 0
Moving on to the FortuneThread class, this is a QThread subclass whose job
is to write the fortune to the connected socket. The class reimplements
QThread::run(), and it has a signal for reporting errors.
\snippet examples/network/threadedfortuneserver/fortunethread.cpp 0
FortuneThread's constructor simply stores the socket descriptor and
fortune text, so that they are available for run() later on.
\snippet examples/network/threadedfortuneserver/fortunethread.cpp 1
The first thing our run() function does is to create a QTcpSocket object
on the stack. What's worth noticing is that we are creating this object
inside the thread, which automatically associates the socket to the
thread's event loop. This ensures that Qt will not try to deliver events
to our socket from the main thread while we are accessing it from
FortuneThread::run().
\snippet examples/network/threadedfortuneserver/fortunethread.cpp 2
The socket is initialized by calling QTcpSocket::setSocketDescriptor(),
passing our socket descriptor as an argument. We expect this to succeed,
but just to be sure, (although unlikely, the system may run out of
resources,) we catch the return value and report any error.
\snippet examples/network/threadedfortuneserver/fortunethread.cpp 3
As with the \l{network/fortuneserver}{Fortune Server} example, we encode
the fortune into a QByteArray using QDataStream.
\snippet examples/network/threadedfortuneserver/fortunethread.cpp 4
But unlike the previous example, we finish off by calling
QTcpSocket::waitForDisconnected(), which blocks the calling thread until
the socket has disconnected. Because we are running in a separate thread,
the GUI will remain responsive.
\sa {Fortune Server Example}, {Fortune Client Example}, {Blocking Fortune
Client Example}
*/
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