| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation (qt-info@nokia.com)
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at qt-info@nokia.com.
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \example network/threadedfortuneserver
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| 30 | \title Threaded Fortune Server Example
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| 31 |
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| 32 | The Threaded Fortune Server example shows how to create a server for a
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| 33 | simple network service that uses threads to handle requests from different
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| 34 | clients. It is intended to be run alongside the Fortune Client example.
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| 35 |
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| 36 | \image threadedfortuneserver-example.png
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| 37 |
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| 38 | The implementation of this example is similar to that of the
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| 39 | \l{network/fortuneserver}{Fortune Server} example, but here we will
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| 40 | implement a subclass of QTcpServer that starts each connection in a
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| 41 | different thread.
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| 42 |
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| 43 | For this we need two classes: FortuneServer, a QTcpServer subclass, and
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| 44 | FortuneThread, which inherits QThread.
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| 45 |
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| 46 | \snippet examples/network/threadedfortuneserver/fortuneserver.h 0
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| 47 |
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| 48 | FortuneServer inherits QTcpServer and reimplements
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| 49 | QTcpServer::incomingConnection(). We also use it for storing the list of
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| 50 | random fortunes.
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| 51 |
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| 52 | \snippet examples/network/threadedfortuneserver/fortuneserver.cpp 0
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| 53 |
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| 54 | We use FortuneServer's constructor to simply generate the list of
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| 55 | fortunes.
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| 56 |
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| 57 | \snippet examples/network/threadedfortuneserver/fortuneserver.cpp 1
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| 58 |
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| 59 | Our implementation of QTcpServer::incomingConnection() creates a
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| 60 | FortuneThread object, passing the incoming socket descriptor and a random
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| 61 | fortune to FortuneThread's constructor. By connecting FortuneThread's
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| 62 | finished() signal to QObject::deleteLater(), we ensure that the thread
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| 63 | gets deleted once it has finished. We can then call QThread::start(),
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| 64 | which starts the thread.
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| 65 |
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| 66 | \snippet examples/network/threadedfortuneserver/fortunethread.h 0
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| 67 |
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| 68 | Moving on to the FortuneThread class, this is a QThread subclass whose job
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| 69 | is to write the fortune to the connected socket. The class reimplements
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| 70 | QThread::run(), and it has a signal for reporting errors.
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| 71 |
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| 72 | \snippet examples/network/threadedfortuneserver/fortunethread.cpp 0
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| 73 |
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| 74 | FortuneThread's constructor simply stores the socket descriptor and
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| 75 | fortune text, so that they are available for run() later on.
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| 76 |
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| 77 | \snippet examples/network/threadedfortuneserver/fortunethread.cpp 1
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| 78 |
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| 79 | The first thing our run() function does is to create a QTcpSocket object
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| 80 | on the stack. What's worth noticing is that we are creating this object
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| 81 | inside the thread, which automatically associates the socket to the
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| 82 | thread's event loop. This ensures that Qt will not try to deliver events
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| 83 | to our socket from the main thread while we are accessing it from
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| 84 | FortuneThread::run().
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| 85 |
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| 86 | \snippet examples/network/threadedfortuneserver/fortunethread.cpp 2
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| 87 |
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| 88 | The socket is initialized by calling QTcpSocket::setSocketDescriptor(),
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| 89 | passing our socket descriptor as an argument. We expect this to succeed,
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| 90 | but just to be sure, (although unlikely, the system may run out of
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| 91 | resources,) we catch the return value and report any error.
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| 92 |
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| 93 | \snippet examples/network/threadedfortuneserver/fortunethread.cpp 3
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| 94 |
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| 95 | As with the \l{network/fortuneserver}{Fortune Server} example, we encode
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| 96 | the fortune into a QByteArray using QDataStream.
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| 97 |
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| 98 | \snippet examples/network/threadedfortuneserver/fortunethread.cpp 4
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| 99 |
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| 100 | But unlike the previous example, we finish off by calling
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| 101 | QTcpSocket::waitForDisconnected(), which blocks the calling thread until
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| 102 | the socket has disconnected. Because we are running in a separate thread,
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| 103 | the GUI will remain responsive.
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| 104 |
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| 105 | \sa {Fortune Server Example}, {Fortune Client Example}, {Blocking Fortune
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| 106 | Client Example}
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| 107 | */
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