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# A simple HTTP daemon

This example shows how to use the QServerSocket class. It is a very simple implementation of a HTTP daemon that listens on port 8080 and sends back a simple HTML page back for every GET request it gets. After sending the page, it closes the connection.

Implementation (httpd.cpp):

    /****************************************************************************
    ** $Id: qt/httpd.cpp   3.3.8   edited Jan 11 14:37 $
    **
    ** Copyright (C) 1992-2007 Trolltech ASA.  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 <stdlib.h>
    #include <qsocket.h>
    #include <qregexp.h>
    #include <qserversocket.h>
    #include <qapplication.h>
    #include <qmainwindow.h>
    #include <qtextstream.h>
    #include <qvbox.h>
    #include <qlabel.h>
    #include <qtextview.h>
    #include <qpushbutton.h>

    // HttpDaemon is the the class that implements the simple HTTP server.
    class HttpDaemon : public QServerSocket
    {
        Q_OBJECT
    public:
        HttpDaemon( QObject* parent=0 ) :
            QServerSocket(8080,1,parent)
        {
            if ( !ok() ) {
                qWarning("Failed to bind to port 8080");
                exit( 1 );
            }
        }

        void newConnection( int socket )
        {
            // When a new client connects, the server constructs a QSocket and all
            // communication with the client is done over this QSocket. QSocket
            // works asynchronouslyl, this means that all the communication is done
            // in the two slots readClient() and discardClient().
            QSocket* s = new QSocket( this );
            connect( s, SIGNAL(readyRead()), this, SLOT(readClient()) );
            connect( s, SIGNAL(delayedCloseFinished()), this, SLOT(discardClient()) );
            s->setSocket( socket );
            emit newConnect();
        }

    signals:
        void newConnect();
        void endConnect();
        void wroteToClient();

    private slots:
        void readClient()
        {
            // This slot is called when the client sent data to the server. The
            // server looks if it was a get request and sends a very simple HTML
            // document back.
            QSocket* socket = (QSocket*)sender();
            if ( socket->canReadLine() ) {
                QStringList tokens = QStringList::split( QRegExp("[ \r\n][ \r\n]*"), socket->readLine() );
                if ( tokens[0] == "GET" ) {
                    QTextStream os( socket );
                    os.setEncoding( QTextStream::UnicodeUTF8 );
                    os << "HTTP/1.0 200 Ok\r\n"
                        "Content-Type: text/html; charset=\"utf-8\"\r\n"
                        "\r\n"
                        "<h1>Nothing to see here</h1>\n";
                    socket->close();
                    emit wroteToClient();
                }
            }
        }
        void discardClient()
        {
            QSocket* socket = (QSocket*)sender();
            delete socket;
            emit endConnect();
        }
    };

    // HttpInfo provides a simple graphical user interface to the server and shows
    // the actions of the server.
    class HttpInfo : public QVBox
    {
        Q_OBJECT
    public:
        HttpInfo()
        {
            HttpDaemon *httpd = new HttpDaemon( this );

            QString itext = QString(
                    "This is a small httpd example.\n"
                    "You can connect with your\n"
                    "web browser to port %1"
                ).arg( httpd->port() );
            QLabel *lb = new QLabel( itext, this );
            lb->setAlignment( AlignHCenter );
            infoText = new QTextView( this );
            QPushButton *quit = new QPushButton( "quit" , this );

            connect( httpd, SIGNAL(newConnect()), SLOT(newConnect()) );
            connect( httpd, SIGNAL(endConnect()), SLOT(endConnect()) );
            connect( httpd, SIGNAL(wroteToClient()), SLOT(wroteToClient()) );
            connect( quit, SIGNAL(pressed()), qApp, SLOT(quit()) );
        }

        ~HttpInfo()
        {
        }

    private slots:
        void newConnect()
        {
            infoText->append( "New connection" );
        }
        void endConnect()
        {
            infoText->append( "Connection closed\n\n" );
        }
        void wroteToClient()
        {
            infoText->append( "Wrote to client" );
        }

    private:
        QTextView *infoText;
    };

    int main( int argc, char** argv )
    {
        QApplication app( argc, argv );
        HttpInfo info;
        app.setMainWidget( &info );
        info.show();
        return app.exec();
    }

    #include "httpd.moc"

See also Network Examples.