Revision control
++ // Copyright (C) 2016 The Qt Company Ltd.
++ // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
++
++ /*!
++ \example fortuneserver
++ \title Fortune Server
++ \examplecategory {Networking}
++ \meta tags {tcp,network,server}
++ \ingroup examples-network
++ \brief Demonstrates how to create a server for a network service.
++
++ This example is intended to be run alongside the
++ \l{fortuneclient}{Fortune Client} example or the
++ \l{blockingfortuneclient}{Blocking Fortune Client} example.
++
++ \image fortuneserver-example.png Screenshot of the Fortune Server example
++
++ It 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{fortuneclient}{Fortune Client}
++ example), before closing the connection.
++
++ \snippet fortuneserver/server.h 0
++
++ The server is implemented using a simple class with only one slot, for
++ handling incoming connections.
++
++ \snippet 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 fortuneserver/server.cpp 2
++
++ Our server generates a list of random fortunes that it can send to
++ connecting clients.
++
++ \snippet 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 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_5_10 to ensure that
++ we can communicate with clients from future versions of Qt (see
++ QDataStream::setVersion()). We continue by streaming in a random fortune.
++
++ \snippet fortuneserver/server.cpp 7
++
++ We then call QTcpServer::nextPendingConnection(), 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 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}, {Threaded Fortune Server}
++ */