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# A simple mail client

This example shows how to use the TQSocket class. The client can only be used to send mails. The interesting part is the implementation of the SMTP protocol.

Header file (smtp.h):

    /****************************************************************************
    ** $Id: qt/smtp.h   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 TQt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #ifndef SMTP_H
    #define SMTP_H

    #include <ntqobject.h>
    #include <ntqstring.h>

    class TQSocket;
    class TQTextStream;
    class TQDns;

    class Smtp : public TQObject
    {
        TQ_OBJECT

    public:
        Smtp( const TQString &from, const TQString &to,
              const TQString &subject, const TQString &body );
        ~Smtp();

    signals:
        void status( const TQString & );

    private slots:
        void dnsLookupHelper();
        void readyRead();
        void connected();

    private:
        enum State {
            Init,
            Mail,
            Rcpt,
            Data,
            Body,
            Quit,
            Close
        };

        TQString message;
        TQString from;
        TQString rcpt;
        TQSocket *socket;
        TQTextStream * t;
        int state;
        TQString response;
        TQDns * mxLookup;
    };

    #endif

Implementation (smtp.cpp):

    /****************************************************************************
    ** $Id: qt/smtp.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 TQt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "smtp.h"

    #include <ntqtextstream.h>
    #include <ntqsocket.h>
    #include <ntqdns.h>
    #include <ntqtimer.h>
    #include <ntqapplication.h>
    #include <ntqmessagebox.h>
    #include <ntqregexp.h>

    Smtp::Smtp( const TQString &from, const TQString &to,
                const TQString &subject,
                const TQString &body )
    {
        socket = new TQSocket( this );
        connect ( socket, SIGNAL( readyRead() ),
                  this, SLOT( readyRead() ) );
        connect ( socket, SIGNAL( connected() ),
                  this, SLOT( connected() ) );

        mxLookup = new TQDns( to.mid( to.find( '@' )+1 ), TQDns::Mx );
        connect( mxLookup, SIGNAL(resultsReady()),
                 this, SLOT(dnsLookupHelper()) );

        message = TQString::fromLatin1( "From: " ) + from +
                  TQString::fromLatin1( "\nTo: " ) + to +
                  TQString::fromLatin1( "\nSubject: " ) + subject +
                  TQString::fromLatin1( "\n\n" ) + body + "\n";
        message.replace( TQString::fromLatin1( "\n" ),
                         TQString::fromLatin1( "\r\n" ) );
        message.replace( TQString::fromLatin1( "\r\n.\r\n" ),
                         TQString::fromLatin1( "\r\n..\r\n" ) );

        this->from = from;
        rcpt = to;

        state = Init;
    }

    Smtp::~Smtp()
    {
        delete t;
        delete socket;
    }

    void Smtp::dnsLookupHelper()
    {
        TQValueList<TQDns::MailServer> s = mxLookup->mailServers();
        if ( s.isEmpty() ) {
            if ( !mxLookup->isWorking() )
                emit status( tr( "Error in MX record lookup" ) );
            return;
        }

        emit status( tr( "Connecting to %1" ).arg( s.first().name ) );

        socket->connectToHost( s.first().name, 25 );
        t = new TQTextStream( socket );
    }

    void Smtp::connected()
    {
        emit status( tr( "Connected to %1" ).arg( socket->peerName() ) );
    }

    void Smtp::readyRead()
    {
        // SMTP is line-oriented
        if ( !socket->canReadLine() )
            return;

        TQString responseLine;
        do {
            responseLine = socket->readLine();
            response += responseLine;
        } while( socket->canReadLine() && responseLine[3] != ' ' );
        responseLine.truncate( 3 );

        if ( state == Init && responseLine[0] == '2' ) {
            // banner was okay, let's go on
            *t << "HELO there\r\n";
            state = Mail;
        } else if ( state == Mail && responseLine[0] == '2' ) {
            // HELO response was okay (well, it has to be)
            *t << "MAIL FROM: <" << from << ">\r\n";
            state = Rcpt;
        } else if ( state == Rcpt && responseLine[0] == '2' ) {
            *t << "RCPT TO: <" << rcpt << ">\r\n";
            state = Data;
        } else if ( state == Data && responseLine[0] == '2' ) {
            *t << "DATA\r\n";
            state = Body;
        } else if ( state == Body && responseLine[0] == '3' ) {
            *t << message << ".\r\n";
            state = Quit;
        } else if ( state == Quit && responseLine[0] == '2' ) {
            *t << "QUIT\r\n";
            // here, we just close.
            state = Close;
            emit status( tr( "Message sent" ) );
        } else if ( state == Close ) {
            deleteLater();
            return;
        } else {
            // something broke.
            TQMessageBox::warning( tqApp->activeWindow(),
                                  tr( "TQt Mail Example" ),
                                  tr( "Unexpected reply from SMTP server:\n\n" ) +
                                  response );
            state = Close;
        }

        response = "";
    }

See also Network Examples.