1 files changed, 15 insertions, 2 deletions
diff --git a/src/serialport/qserialport_win.cpp b/src/serialport/qserialport_win.cpp
index 6d5dac0..e356e4c 100644
--- a/src/serialport/qserialport_win.cpp
+++ b/src/serialport/qserialport_win.cpp
@@ -437,10 +437,13 @@ bool QSerialPortPrivate::completeAsyncRead(qint64 bytesTransferred)
     readStarted = false;
 
     bool result = true;
-    if (bytesTransferred == ReadChunkSize)
+    if (bytesTransferred == ReadChunkSize
+            || queuedBytesCount(QSerialPort::Input) > 0) {
         result = startAsyncRead();
-    else if (readBufferMaxSize == 0 || readBufferMaxSize > buffer.size())
+    } else if (readBufferMaxSize == 0
+               || readBufferMaxSize > buffer.size()) {
         result = startAsyncCommunication();
+    }
 
     if (bytesTransferred > 0)
         emitReadyRead();
@@ -598,6 +601,16 @@ OVERLAPPED *QSerialPortPrivate::waitForNotified(int msecs)
     return overlapped;
 }
 
+qint64 QSerialPortPrivate::queuedBytesCount(QSerialPort::Direction direction) const
+{
+    COMSTAT comstat;
+    if (::ClearCommError(handle, Q_NULLPTR, &comstat) == 0)
+        return -1;
+    return (direction == QSerialPort::Input)
+            ? comstat.cbInQue
+            : ((direction == QSerialPort::Output) ? comstat.cbOutQue : -1);
+}
+
 inline bool QSerialPortPrivate::initialize()
 {
     Q_Q(QSerialPort);