/**************************************************************************** ** ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). ** All rights reserved. ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** GNU Free Documentation License ** 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. ** ** Other Usage ** Alternatively, this file may be used in accordance with the terms ** and conditions contained in a signed written agreement between you ** and Nokia. ** ** ** ** ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \example network/fortuneserver \title Fortune Server Example The Fortune Server example shows how to create a server for a simple network service. It is intended to be run alongside the \l{network/fortuneclient}{Fortune Client} example or the \l{network/blockingfortuneclient}{Blocking Fortune Client} example. \image fortuneserver-example.png Screenshot of the Fortune Server example This example uses QTcpServer to accept incoming TCP connections, and a simple QDataStream based data transfer protocol to write a fortune to the connecting client (from the \l{network/fortuneclient}{Fortune Client} example), before closing the connection. \snippet examples/network/fortuneserver/server.h 0 The server is implemented using a simple class with only one slot, for handling incoming connections. \snippet examples/network/fortuneserver/server.cpp 1 In its constructor, our Server object calls QTcpServer::listen() to set up a QTcpServer to listen on all addresses, on an arbitrary port. In then displays the port QTcpServer picked in a label, so that user knows which port the fortune client should connect to. \snippet examples/network/fortuneserver/server.cpp 2 Our server generates a list of random fortunes that is can send to connecting clients. \snippet examples/network/fortuneserver/server.cpp 3 When a client connects to our server, QTcpServer will emit QTcpServer::newConnection(). In turn, this will invoke our sendFortune() slot: \snippet examples/network/fortuneserver/server.cpp 4 The purpose of this slot is to select a random line from our list of fortunes, encode it into a QByteArray using QDataStream, and then write it to the connecting socket. This is a common way to transfer binary data using QTcpSocket. First we create a QByteArray and a QDataStream object, passing the bytearray to QDataStream's constructor. We then explicitly set the protocol version of QDataStream to QDataStream::Qt_4_0 to ensure that we can communicate with clients from future versions of Qt. (See QDataStream::setVersion().) \snippet examples/network/fortuneserver/server.cpp 6 At the start of our QByteArray, we reserve space for a 16 bit integer that will contain the total size of the data block we are sending. We continue by streaming in a random fortune. Then we seek back to the beginning of the QByteArray, and overwrite the reserved 16 bit integer value with the total size of the array. By doing this, we provide a way for clients to verify how much data they can expect before reading the whole packet. \snippet examples/network/fortuneserver/server.cpp 7 We then call QTcpServer::newPendingConnection(), which returns the QTcpSocket representing the server side of the connection. By connecting QTcpSocket::disconnected() to QObject::deleteLater(), we ensure that the socket will be deleted after disconnecting. \snippet examples/network/fortuneserver/server.cpp 8 The encoded fortune is written using QTcpSocket::write(), and we finally call QTcpSocket::disconnectFromHost(), which will close the connection after QTcpSocket has finished writing the fortune to the network. Because QTcpSocket works asynchronously, the data will be written after this function returns, and control goes back to Qt's event loop. The socket will then close, which in turn will cause QObject::deleteLater() to delete it. \sa {Fortune Client Example}, {Threaded Fortune Server Example} */