Question

This example shows how to implement your own QNetworkProtocol. The protocol that was chosen for this example is NTTP. Please note that this implementation is very simple since it is designed to be an example. It should not be used as a real NNTP implemention.

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Header file (nntp.h):

/****************************************************************************
** $Id:  qt/nntp.h   3.0.5   edited Oct 12 2001 $
**
** 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.
**
*****************************************************************************/

#ifndef NNTP_H
#define NNTP_H

#include <qsocket.h>
#include <qnetworkprotocol.h>

class Nntp : public QNetworkProtocol
{
    Q_OBJECT

public:
    Nntp();
    virtual ~Nntp();
    virtual int supportedOperations() const;

protected:
    virtual void operationListChildren( QNetworkOperation *op );
    virtual void operationGet( QNetworkOperation *op );

    QSocket *commandSocket;
    bool connectionReady;
    bool readGroups;
    bool readArticle;

private:
    bool checkConnection( QNetworkOperation *op );
    void close();
    void parseGroups();
    void parseArticle();

protected slots:
    void hostFound();
    void connected();
    void closed();
    void readyRead();
    void error( int );

};

#endif

---

Implementation (nntp.cpp):

/****************************************************************************
** $Id:  qt/nntp.cpp   3.0.5   edited Oct 12 2001 $
**
** 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 "nntp.h"
#include <qurlinfo.h>
#include <stdlib.h>
#include <qurloperator.h>
#include <qstringlist.h>
#include <qregexp.h>

Nntp::Nntp()
    : QNetworkProtocol(), connectionReady( FALSE ),
      readGroups( FALSE ), readArticle( FALSE )
{
    // create the command socket and connect to its signals
    commandSocket = new QSocket( this );
    connect( commandSocket, SIGNAL( hostFound() ),
             this, SLOT( hostFound() ) );
    connect( commandSocket, SIGNAL( connected() ),
             this, SLOT( connected() ) );
    connect( commandSocket, SIGNAL( connectionClosed() ),
             this, SLOT( closed() ) );
    connect( commandSocket, SIGNAL( readyRead() ),
             this, SLOT( readyRead() ) );
    connect( commandSocket, SIGNAL( error( int ) ),
             this, SLOT( error( int ) ) );
}

Nntp::~Nntp()
{
    close();
    delete commandSocket;
}

void Nntp::operationListChildren( QNetworkOperation * )
{
    // create a command
    QString path = url()->path(), cmd;
    if ( path.isEmpty() || path == "/" ) {
        // if the path is empty or we are in the root dir,
        // we want to read the list of available newsgroups
        cmd = "list newsgroups\r\n";
    } else if ( url()->isDir() ) {
        // if the path is a directory (in our case a news group)
        // we want to list the articles of this group
        path = path.replace( QRegExp( "/" ), "" );
        cmd = "listgroup " + path + "\r\n";
    } else
        return;

    // write the command to the socket
    commandSocket->writeBlock( cmd.latin1(), cmd.length() );
    readGroups = TRUE;
}

void Nntp::operationGet( QNetworkOperation *op )
{
    // get the dirPath of the URL (this is our news group)
    // and the filename (which is the article we want to read)
    QUrl u( op->arg( 0 ) );
    QString dirPath = u.dirPath(), file = u.fileName();
    dirPath = dirPath.replace( QRegExp( "/" ), "" );

    // go to the group in which the article is
    QString cmd;
    cmd = "group " + dirPath + "\r\n";
    commandSocket->writeBlock( cmd.latin1(), cmd.length() );

    // read the head of the article
    cmd = "article " + file + "\r\n";
    commandSocket->writeBlock( cmd.latin1(), cmd.length() );
    readArticle = TRUE;
}

bool Nntp::checkConnection( QNetworkOperation * )
{
    // we are connected, return TRUE
    if ( commandSocket->isOpen() && connectionReady )
        return TRUE;

    // seems that there is no chance to connect
    if ( commandSocket->isOpen() )
        return FALSE;

    // don't call connectToHost() if we are already trying to connect
    if ( commandSocket->state() == QSocket::Connecting )
        return FALSE;

    // start connecting
    connectionReady = FALSE;
    commandSocket->connectToHost( url()->host(),
                                  url()->port() != -1 ? url()->port() : 119 );
    return FALSE;
}

void Nntp::close()
{
    // close the command socket
    if ( commandSocket->isOpen() ) {
        commandSocket->writeBlock( "quit\r\n", strlen( "quit\r\n" ) );
        commandSocket->close();
    }
}

int Nntp::supportedOperations() const
{
    // we only support listing children and getting data
    return OpListChildren | OpGet;
}

void Nntp::hostFound()
{
    if ( url() )
        emit connectionStateChanged( ConHostFound, tr( "Host %1 found" ).arg( url()->host() ) );
    else
        emit connectionStateChanged( ConHostFound, tr( "Host found" ) );
}

void Nntp::connected()
{
    if ( url() )
        emit connectionStateChanged( ConConnected, tr( "Connected to host %1" ).arg( url()->host() ) );
    else
        emit connectionStateChanged( ConConnected, tr( "Connected to host" ) );
}

void Nntp::closed()
{
    if ( url() )
        emit connectionStateChanged( ConClosed, tr( "Connection to %1 closed" ).arg( url()->host() ) );
    else
        emit connectionStateChanged( ConClosed, tr( "Connection closed" ) );
}

void Nntp::readyRead()
{
    // new data arrived on the command socket

    // of we should read the list of available groups, let's do so
    if ( readGroups ) {
        parseGroups();
        return;
    }

    // of we should read an article, let's do so
    if ( readArticle ) {
        parseArticle();
        return;
    }

    // read the new data from the socket
    QCString s;
    s.resize( commandSocket->bytesAvailable() );
    commandSocket->readBlock( s.data(), commandSocket->bytesAvailable() );

    if ( !url() )
        return;

    // of the code of the server response was 200, we know that the
    // server is ready to get commands from us now
    if ( s.left( 3 ) == "200" )
        connectionReady = TRUE;
}

void Nntp::parseGroups()
{
    if ( !commandSocket->canReadLine() )
        return;

    // read one line after the other
    while ( commandSocket->canReadLine() ) {
        QString s = commandSocket->readLine();

        // if the  line starts with a dot, all groups or articles have been listed,
        // so we finished processing the listChildren() command
        if ( s[ 0 ] == '.' ) {
            readGroups = FALSE;
            operationInProgress()->setState( StDone );
            emit finished( operationInProgress() );
            return;
        }

        // if the code of the server response is 215 or 211
        // the next line will be the first group or article (depending on what we read).
        // So let others know that we start reading now...
        if ( s.left( 3 ) == "215" || s.left( 3 ) == "211" ) {
            operationInProgress()->setState( StInProgress );
            emit start( operationInProgress() );
            continue;
        }

        // parse the line and create a QUrlInfo object
        // which describes the child (group or article)
        bool tab = s.find( '\t' ) != -1;
        QString group = s.mid( 0, s.find( tab ? '\t' : ' ' ) );
        QUrlInfo inf;
        inf.setName( group );
        QString path = url()->path();
        inf.setDir( path.isEmpty() || path == "/" );
        inf.setSymLink( FALSE );
        inf.setFile( !inf.isDir() );
        inf.setWritable( FALSE );
        inf.setReadable( TRUE );

        // let others know about our new child
        emit newChild( inf, operationInProgress() );
    }

}

void Nntp::parseArticle()
{
    if ( !commandSocket->canReadLine() )
        return;

    // read an article one line after the other
    while ( commandSocket->canReadLine() ) {
        QString s = commandSocket->readLine();

        // if the  line starts with a dot, we finished reading something
        if ( s[ 0 ] == '.' ) {
            readArticle = FALSE;
            operationInProgress()->setState( StDone );
            emit finished( operationInProgress() );
            return;
        }

        if ( s.right( 1 ) == "\n" )
            s.remove( s.length() - 1, 1 );

        // emit the new data of the article which we read
        emit data( QCString( s.ascii() ), operationInProgress() );
    }
}

void Nntp::error( int code )
{
    if ( code == QSocket::ErrHostNotFound ||
         code == QSocket::ErrConnectionRefused ) {
        // this signal is called if connecting to the server failed
        if ( operationInProgress() ) {
            QString msg = tr( "Host not found or couldn't connect to: \n" + url()->host() );
            operationInProgress()->setState( StFailed );
            operationInProgress()->setProtocolDetail( msg );
            operationInProgress()->setErrorCode( (int)ErrHostNotFound );
            clearOperationQueue();
            emit finished( operationInProgress() );
        }
    }
}

See also Network Examples.