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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\example network/threadedfortuneserver
\title Threaded Fortune Server Example
\brief 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.
The example 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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