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A small client-server example

This example shows how two programs can communicate using sockets. It consists out of two different programs: a server and a client.

The server listens on port number 4242 and accepts incoming connections. It sends back every line he receives from the client. The line is prepended with the line number.

The client tries to connect to the server on the host specified on the command line or to localhost if no command line arguments are specified. You can send single lines to the server.


Implementation server (server.cpp):




Implementation client (client.cpp):

/****************************************************************************
** $Id:  qt/client.cpp   3.0.0-beta2   edited Jun 1 18:44 $
**
** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
**
** This file is part of an example program for Qt.  This example
** program may be used, distributed and modified without limitation.
**
*****************************************************************************/

#include <qsocket.h>
#include <qapplication.h>
#include <qvbox.h>
#include <qhbox.h>
#include <qtextview.h>
#include <qlineedit.h>
#include <qlabel.h>
#include <qpushbutton.h>
#include <qtextstream.h>


class Client : public QVBox
{
    Q_OBJECT
public:
    Client( const QString &host, Q_UINT16 port )
    {
        // GUI layout
        infoText = new QTextView( this );
        QHBox *hb = new QHBox( this );
        inputText = new QLineEdit( hb );
        QPushButton *send = new QPushButton( tr("Send") , hb );
        QPushButton *close = new QPushButton( tr("Close connection") , this );
        QPushButton *quit = new QPushButton( tr("Quit") , this );

        connect( send, SIGNAL(clicked()), SLOT(sendToServer()) );
        connect( close, SIGNAL(clicked()), SLOT(closeConnection()) );
        connect( quit, SIGNAL(clicked()), qApp, SLOT(quit()) );

        // create the socket and connect various of its signals
        socket = new QSocket( this );
        connect( socket, SIGNAL(connected()),
                SLOT(socketConnected()) );
        connect( socket, SIGNAL(connectionClosed()),
                SLOT(socketConnectionClosed()) );
        connect( socket, SIGNAL(readyRead()),
                SLOT(socketReadyRead()) );
        connect( socket, SIGNAL(error(int)),
                SLOT(socketError(int)) );

        // connect to the server
        infoText->append( tr("Try to connect to server\n") );
        socket->connectToHost( host, port );
    }

    ~Client()
    {
    }

private slots:
    void closeConnection()
    {
        socket->close();
        if ( socket->state() == QSocket::Closing ) {
            // We have a delayed close.
            connect( socket, SIGNAL(delayedCloseFinished()),
                    SLOT(socketClosed()) );
        } else {
            // The socket is closed.
            socketClosed();
        }
    }

    void sendToServer()
    {
        // write to the server
        QTextStream os(socket);
        os << inputText->text() << "\n";
        inputText->setText( "" );
    }

    void socketReadyRead()
    {
        // read from the server
        while ( socket->canReadLine() ) {
            infoText->append( socket->readLine() );
        }
    }

    void socketConnected()
    {
        infoText->append( tr("Connected to server\n") );
    }

    void socketConnectionClosed()
    {
        infoText->append( tr("Connection closed by the server\n") );
    }

    void socketClosed()
    {
        infoText->append( tr("Connection closed\n") );
    }

    void socketError( int e )
    {
        infoText->append( tr("Error number %1 occurred\n").arg(e) );
    }

private:
    QSocket *socket;
    QTextView *infoText;
    QLineEdit *inputText;
};


int main( int argc, char** argv )
{
    QApplication app( argc, argv );
    Client client( argc<2 ? "localhost" : argv[1], 4242 );
    app.setMainWidget( &client );
    client.show();
    return app.exec();
}

#include "client.moc"


Copyright © 2001 TrolltechTrademarks
Qt version 3.0.0-beta2