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diff --git a/doc/src/porting/qt4-network.qdoc b/doc/src/porting/qt4-network.qdoc new file mode 100644 index 0000000..475aba1 --- /dev/null +++ b/doc/src/porting/qt4-network.qdoc @@ -0,0 +1,229 @@ +/**************************************************************************** +** +** 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. +** +** $QT_BEGIN_LICENSE:FDL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** 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. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \page qt4-network.html + \title The Network Module in Qt 4 + + \contentspage {What's New in Qt 4}{Home} + \previouspage The Qt 4 Database GUI Layer + \nextpage The Qt 4 Style API + + The network module in Qt 4 provides some new features, such as + support for internationalized domain names, better IPv6 support, + and better performance. And since Qt 4 allows us to break binary + compatibility with previous releases, we took this opportunity to + improve the class names and API to make them more intuitive to + use. + + \tableofcontents + + \section1 General Overview + + Compared to Qt 3, the network module in Qt 4 brings the following + benefits: + + \list + \o The Qt 4 network classes have more intuitive names and APIs. + For example, QServerSocket has been renamed QTcpServer. + \o The entire network module is \l{reentrant}, making it + possible to use them simultaneously from multiple threads. + \o It is now possible to send and receive UDP datagrams and to + use synchronous (i.e., blocking) sockets without having to + use a low-level API (QSocketDevice in Qt 3). + \o QHostAddress and QHostInfo support internationalized domain names + (RFC 3492). + \o QUrl is more lightweight and fully supports the latest URI + specification draft. + \o UDP broadcasting is now supported. + \endlist + + The Qt 4 network module provides fundamental classes for writing + TCP and UDP applications, as well as higher-level classes that + implement the client side of the HTTP and FTP protocols. + + Here's an overview of the TCP and UDP classes: + + \list + \o QTcpSocket encapsulates a TCP socket. It inherits from + QIODevice, so you can use QTextStream and QDataStream to read + or write data. It is useful for writing both clients and + servers. + \o QTcpServer allows you to listen on a certain port on a + server. It emits a + \l{QTcpServer::newConnection()}{newConnection()} signal every + time a client tries to connect to the server. Once the + connection is established, you can talk to the client using + QTcpSocket. + \o QUdpSocket is an API for sending and receiving UDP datagrams. + \endlist + + QTcpSocket and QUdpSocket inherit most of their functionality + from QAbstractSocket. You can also use QAbstractSocket directly + as a wrapper around a native socket descriptor. + + By default, the socket classes work asynchronously (i.e., they + are non-blocking), emitting signals to notify when data has + arrived or when the peer has closed the connection. In + multithreaded applications and in non-GUI applications, you also + have the opportunity of using blocking (synchronous) functions on + the socket, which often results in a more straightforward style + of programming, with the networking logic concentrated in one or + two functions instead of spread across multiple slots. + + QFtp and QNetworkAccessManager and its associated classes use + QTcpSocket internally to implement the FTP and HTTP protocols. The + classes work asynchronously and can schedule (i.e., queue) + requests. + + The network module contains four helper classes: QHostAddress, + QHostInfo, QUrl, and QUrlInfo. QHostAddress stores an IPv4 or IPv6 + address, QHostInfo resolves host names into addresses, QUrl stores a + URL, and QUrlInfo stores information about a resource pointed to + by a URL, such as the file size and modification date. (Because + QUrl is used by QTextBrowser, it is part of the QtCore library and + not of QtNetwork.) + + See the \l QtNetwork module overview for more information. + + \section1 Example Code + + All the code snippets presented here are quoted from + self-contained, compilable examples located in Qt's \c + examples/network directory. + + \section2 TCP Client + + The first example illustrates how to write a TCP client using + QTcpSocket. The client talks to a fortune server that provides + fortune to the user. Here's how to set up the socket: + + \snippet examples/network/fortuneclient/client.cpp 1 + \codeline + \snippet examples/network/fortuneclient/client.cpp 2 + \snippet examples/network/fortuneclient/client.cpp 4 + + When the user requests a new fortune, the client establishes a + connection to the server: + + \snippet examples/network/fortuneclient/client.cpp 7 + + When the server answers, the following code is executed to read + the data from the socket: + + \snippet examples/network/fortuneclient/client.cpp 9 + + The server's answer starts with a \e size field (which we store + in \c blockSize), followed by \e size bytes of data. If the + client hasn't received all the data yet, it waits for the server + to send more. + + An alternative approach is to use a blocking socket. The code can + then be concentrated in one function: + + \snippet examples/network/blockingfortuneclient/fortunethread.cpp 7 + + \section2 TCP Server + + The following code snippets illustrate how to write a TCP server + using QTcpServer and QTcpSocket. Here's how to set up a TCP + server: + + \snippet examples/network/fortuneserver/server.cpp 0 + \codeline + \snippet examples/network/fortuneserver/server.cpp 3 + + When a client tries to connect to the server, the following code + in the sendFortune() slot is executed: + + \snippet examples/network/fortuneserver/server.cpp 5 + + \section2 UDP Senders and Receivers + + Here's how to broadcast a UDP datagram: + + \snippet examples/network/broadcastsender/sender.cpp 0 + \snippet examples/network/broadcastsender/sender.cpp 1 + + Here's how to receive a UDP datagram: + + \snippet examples/network/broadcastreceiver/receiver.cpp 0 + \codeline + \snippet examples/network/broadcastreceiver/receiver.cpp 1 + + Then in the processPendingDatagrams() slot: + + \snippet examples/network/broadcastreceiver/receiver.cpp 2 + + \section1 Comparison with Qt 3 + + The main difference between Qt 3 and Qt 4 is that the very high + level QNetworkProtocol and QUrlOperator abstraction has been + eliminated. These classes attempted the impossible (unify FTP and + HTTP under one roof), and unsurprisingly failed at that. Qt 4 + still provides QFtp, and it also provides the QNetworkAccessManager. + + The QSocket class in Qt 3 has been renamed QTcpSocket. The new + class is reentrant and supports blocking. It's also easier to + handle closing than with Qt 3, where you had to connect to both + the QSocket::connectionClosed() and the + QSocket::delayedCloseFinished() signals. + + The QServerSocket class in Qt 3 has been renamed QTcpServer. The + API has changed quite a bit. While in Qt 3 it was necessary to + subclass QServerSocket and reimplement the newConnection() pure + virtual function, QTcpServer now emits a + \l{QTcpServer::newConnection()}{newConnection()} signal that you + can connect to a slot. + + The QHostInfo class has been redesigned to use the operating system's + getaddrinfo() function instead of implementing the DNS protocol. + Internally, QHostInfo simply starts a thread and calls getaddrinfo() + in that thread. This wasn't possible in Qt 3 because + getaddrinfo() is a blocking call and Qt 3 could be configured + without multithreading support. + + The QSocketDevice class in Qt 3 is no longer part of the public + Qt API. If you used QSocketDevice to send or receive UDP + datagrams, use QUdpSocket instead. If you used QSocketDevice + because it supported blocking sockets, use QTcpSocket or + QUdpSocket instead and use the blocking functions + (\l{QAbstractSocket::waitForConnected()}{waitForConnected()}, + \l{QAbstractSocket::waitForConnected()}{waitForReadyRead()}, + etc.). If you used QSocketDevice from a non-GUI thread because it + was the only reentrant networking class in Qt 3, use QTcpSocket, + QTcpServer, or QUdpSocket instead. + + Internally, Qt 4 has a class called QSocketLayer that provides a + cross-platform low-level socket API. It resembles the old + QSocketDevice class. We might make it public in a later release + if users ask for it. + + As an aid to porting to Qt 4, the \l{Qt3Support} + library includes Q3Dns, Q3ServerSocket, Q3Socket, and Q3SocketDevice + classes. +*/ |