|
1 /**************************************************************************** |
|
2 ** |
|
3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
|
4 ** All rights reserved. |
|
5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
|
6 ** |
|
7 ** This file is part of the documentation of the Qt Toolkit. |
|
8 ** |
|
9 ** $QT_BEGIN_LICENSE:LGPL$ |
|
10 ** No Commercial Usage |
|
11 ** This file contains pre-release code and may not be distributed. |
|
12 ** You may use this file in accordance with the terms and conditions |
|
13 ** contained in the Technology Preview License Agreement accompanying |
|
14 ** this package. |
|
15 ** |
|
16 ** GNU Lesser General Public License Usage |
|
17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
|
18 ** General Public License version 2.1 as published by the Free Software |
|
19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
|
20 ** packaging of this file. Please review the following information to |
|
21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
|
22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
|
23 ** |
|
24 ** In addition, as a special exception, Nokia gives you certain additional |
|
25 ** rights. These rights are described in the Nokia Qt LGPL Exception |
|
26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. |
|
27 ** |
|
28 ** If you have questions regarding the use of this file, please contact |
|
29 ** Nokia at qt-info@nokia.com. |
|
30 ** |
|
31 ** |
|
32 ** |
|
33 ** |
|
34 ** |
|
35 ** |
|
36 ** |
|
37 ** |
|
38 ** $QT_END_LICENSE$ |
|
39 ** |
|
40 ****************************************************************************/ |
|
41 |
|
42 /*! |
|
43 \example network/fortuneserver |
|
44 \title Fortune Server Example |
|
45 |
|
46 The Fortune Server example shows how to create a server for a simple |
|
47 network service. It is intended to be run alongside the |
|
48 \l{network/fortuneclient}{Fortune Client} example or the |
|
49 \l{network/blockingfortuneclient}{Blocking Fortune Client} example. |
|
50 |
|
51 \image fortuneserver-example.png Screenshot of the Fortune Server example |
|
52 |
|
53 This example uses QTcpServer to accept incoming TCP connections, and a |
|
54 simple QDataStream based data transfer protocol to write a fortune to the |
|
55 connecting client (from the \l{network/fortuneclient}{Fortune Client} |
|
56 example), before closing the connection. |
|
57 |
|
58 \snippet examples/network/fortuneserver/server.h 0 |
|
59 |
|
60 The server is implemented using a simple class with only one slot, for |
|
61 handling incoming connections. |
|
62 |
|
63 \snippet examples/network/fortuneserver/server.cpp 1 |
|
64 |
|
65 In its constructor, our Server object calls QTcpServer::listen() to set up |
|
66 a QTcpServer to listen on all addresses, on an arbitrary port. In then |
|
67 displays the port QTcpServer picked in a label, so that user knows which |
|
68 port the fortune client should connect to. |
|
69 |
|
70 \snippet examples/network/fortuneserver/server.cpp 2 |
|
71 |
|
72 Our server generates a list of random fortunes that is can send to |
|
73 connecting clients. |
|
74 |
|
75 \snippet examples/network/fortuneserver/server.cpp 3 |
|
76 |
|
77 When a client connects to our server, QTcpServer will emit |
|
78 QTcpServer::newConnection(). In turn, this will invoke our |
|
79 sendFortune() slot: |
|
80 |
|
81 \snippet examples/network/fortuneserver/server.cpp 4 |
|
82 |
|
83 The purpose of this slot is to select a random line from our list of |
|
84 fortunes, encode it into a QByteArray using QDataStream, and then write it |
|
85 to the connecting socket. This is a common way to transfer binary data |
|
86 using QTcpSocket. First we create a QByteArray and a QDataStream object, |
|
87 passing the bytearray to QDataStream's constructor. We then explicitly set |
|
88 the protocol version of QDataStream to QDataStream::Qt_4_0 to ensure that |
|
89 we can communicate with clients from future versions of Qt. (See |
|
90 QDataStream::setVersion().) |
|
91 |
|
92 \snippet examples/network/fortuneserver/server.cpp 6 |
|
93 |
|
94 At the start of our QByteArray, we reserve space for a 16 bit integer that |
|
95 will contain the total size of the data block we are sending. We continue |
|
96 by streaming in a random fortune. Then we seek back to the beginning of |
|
97 the QByteArray, and overwrite the reserved 16 bit integer value with the |
|
98 total size of the array. By doing this, we provide a way for clients to |
|
99 verify how much data they can expect before reading the whole packet. |
|
100 |
|
101 \snippet examples/network/fortuneserver/server.cpp 7 |
|
102 |
|
103 We then call QTcpServer::newPendingConnection(), which returns the |
|
104 QTcpSocket representing the server side of the connection. By connecting |
|
105 QTcpSocket::disconnected() to QObject::deleteLater(), we ensure that the |
|
106 socket will be deleted after disconnecting. |
|
107 |
|
108 \snippet examples/network/fortuneserver/server.cpp 8 |
|
109 |
|
110 The encoded fortune is written using QTcpSocket::write(), and we finally |
|
111 call QTcpSocket::disconnectFromHost(), which will close the connection |
|
112 after QTcpSocket has finished writing the fortune to the network. Because |
|
113 QTcpSocket works asynchronously, the data will be written after this |
|
114 function returns, and control goes back to Qt's event loop. The socket |
|
115 will then close, which in turn will cause QObject::deleteLater() to delete |
|
116 it. |
|
117 |
|
118 \sa {Fortune Client Example}, {Threaded Fortune Server Example} |
|
119 */ |