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   3.3.7   edited Aug 31 2005 $
**
** Copyright (C) 1992-2005 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 <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.