| 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/fortuneserver
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| 30 | \title Fortune Server Example
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| 31 |
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| 32 | The Fortune Server example shows how to create a server for a simple
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| 33 | network service. It is intended to be run alongside the
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| 34 | \l{network/fortuneclient}{Fortune Client} example or the
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| 35 | \l{network/blockingfortuneclient}{Blocking Fortune Client} example.
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| 36 |
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| 37 | \image fortuneserver-example.png Screenshot of the Fortune Server example
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| 38 |
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| 39 | This example uses QTcpServer to accept incoming TCP connections, and a
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| 40 | simple QDataStream based data transfer protocol to write a fortune to the
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| 41 | connecting client (from the \l{network/fortuneclient}{Fortune Client}
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| 42 | example), before closing the connection.
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| 43 |
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| 44 | \snippet examples/network/fortuneserver/server.h 0
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| 45 |
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| 46 | The server is implemented using a simple class with only one slot, for
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| 47 | handling incoming connections.
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| 48 |
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| 49 | \snippet examples/network/fortuneserver/server.cpp 1
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| 50 |
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| 51 | In its constructor, our Server object calls QTcpServer::listen() to set up
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| 52 | a QTcpServer to listen on all addresses, on an arbitrary port. In then
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| 53 | displays the port QTcpServer picked in a label, so that user knows which
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| 54 | port the fortune client should connect to.
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| 55 |
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| 56 | \snippet examples/network/fortuneserver/server.cpp 2
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| 57 |
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| 58 | Our server generates a list of random fortunes that is can send to
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| 59 | connecting clients.
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| 60 |
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| 61 | \snippet examples/network/fortuneserver/server.cpp 3
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| 62 |
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| 63 | When a client connects to our server, QTcpServer will emit
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| 64 | QTcpServer::newConnection(). In turn, this will invoke our
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| 65 | sendFortune() slot:
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| 66 |
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| 67 | \snippet examples/network/fortuneserver/server.cpp 4
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| 68 |
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| 69 | The purpose of this slot is to select a random line from our list of
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| 70 | fortunes, encode it into a QByteArray using QDataStream, and then write it
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| 71 | to the connecting socket. This is a common way to transfer binary data
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| 72 | using QTcpSocket. First we create a QByteArray and a QDataStream object,
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| 73 | passing the bytearray to QDataStream's constructor. We then explicitly set
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| 74 | the protocol version of QDataStream to QDataStream::Qt_4_0 to ensure that
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| 75 | we can communicate with clients from future versions of Qt. (See
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| 76 | QDataStream::setVersion().)
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| 77 |
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| 78 | \snippet examples/network/fortuneserver/server.cpp 6
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| 79 |
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| 80 | At the start of our QByteArray, we reserve space for a 16 bit integer that
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| 81 | will contain the total size of the data block we are sending. We continue
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| 82 | by streaming in a random fortune. Then we seek back to the beginning of
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| 83 | the QByteArray, and overwrite the reserved 16 bit integer value with the
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| 84 | total size of the array. By doing this, we provide a way for clients to
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| 85 | verify how much data they can expect before reading the whole packet.
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| 86 |
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| 87 | \snippet examples/network/fortuneserver/server.cpp 7
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| 88 |
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| 89 | We then call QTcpServer::newPendingConnection(), which returns the
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| 90 | QTcpSocket representing the server side of the connection. By connecting
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| 91 | QTcpSocket::disconnected() to QObject::deleteLater(), we ensure that the
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| 92 | socket will be deleted after disconnecting.
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| 93 |
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| 94 | \snippet examples/network/fortuneserver/server.cpp 8
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| 95 |
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| 96 | The encoded fortune is written using QTcpSocket::write(), and we finally
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| 97 | call QTcpSocket::disconnectFromHost(), which will close the connection
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| 98 | after QTcpSocket has finished writing the fortune to the network. Because
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| 99 | QTcpSocket works asynchronously, the data will be written after this
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| 100 | function returns, and control goes back to Qt's event loop. The socket
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| 101 | will then close, which in turn will cause QObject::deleteLater() to delete
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| 102 | it.
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| 103 |
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| 104 | \sa {Fortune Client Example}, {Threaded Fortune Server Example}
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| 105 | */
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