QUdpSocket understanding

[ale301168]

Here is the code I'm using:

lOldFlags = 0;
 
/*
** Forever loop
*/
for (;;)
{
    msleep (100);
 
    /*
    ** Process any datagrams in the queue
    */
    while (cSocket.hasPendingDatagrams ())
    {
      lDgram.resize (cSocket.pendingDatagramSize ());
      cSocket.readDatagram (lDgram.data (), lDgram.size (), &lPeer, &lPort);                
 
     /* ... process the datagram ... */
    }
 
 
    /*
    ** Check for unplugged network cable. When the network cable is
    ** unplugged and plugged again the socket stops receiving datagrams. 
    ** The following code detects the event and calls "bind". This is the
    ** point where the socket is bound the first time because lOldFlags is
    ** initialize to zero
    */
    QNetworkInterface lIf (QNetworkInterface::interfaceFromName (cAdapterName));
    if (lOldFlags != lIf.flags ())                 /* ... if there has been any change in the interface status ... */
    {
       lOldFlags = lIf.flags ();
       if (lIf.flags () & 0x02)                      /* ... if the interface is running ... */
       {
           cSocket.disconnectFromHost ();
           #if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
           if (!cSocket.bind (QHostAddress ("0.0.0.0"), 65000, QUdpSocket::ReuseAddressHint))
           #else
           if (!cSocket.bind (QHostAddress ("0.0.0.0"), 65000, QUdpSocket::ShareAddress))            
           #endif
             lOldFlags = 0;
           else
           {
             int lTTL = 1;
             ip_mreq lMReq;
             memset ((void *) &lMReq, 0, sizeof (lMReq));
             lMReq.imr_multiaddr.s_addr = _HTONL (QHostAddress ("239.0.0.104").toIPv4Address ());
             lMReq.imr_interface.s_addr = _HTONL (QHostAddress ("0.0.0.0").toIPv4Address ());
             if (setsockopt (cSocket.socketDescriptor (), IPPROTO_IP, IP_ADD_MEMBERSHIP, (const char *) &lMReq, sizeof (lMReq)) < 0) lOldFlags = 0;
             if (setsockopt (cSocket.socketDescriptor (), IPPROTO_IP, IP_MULTICAST_TTL, (const char *) &lTTL, sizeof (lTTL)) < 0)  lOldFlags = 0;
           }
       }
    }
 
 
    /*
    ** If there are the conditions write a datagram ...
    */
    /* ... some code here to detect the conditions ... */
   cSocket.writeDatagram (lMsg.data (), lMsg.size (), QHostAddress ("239.0.0.104"), 65000);
 
} /* end forevere loop */

lOldFlags = 0;

/*
** Forever loop
*/
for (;;)
{
    msleep (100);

    /*
    ** Process any datagrams in the queue
    */
    while (cSocket.hasPendingDatagrams ())
    {
      lDgram.resize (cSocket.pendingDatagramSize ());
      cSocket.readDatagram (lDgram.data (), lDgram.size (), &lPeer, &lPort);                

     /* ... process the datagram ... */
    }
    
    
    /*
    ** Check for unplugged network cable. When the network cable is
    ** unplugged and plugged again the socket stops receiving datagrams. 
    ** The following code detects the event and calls "bind". This is the
    ** point where the socket is bound the first time because lOldFlags is
    ** initialize to zero
    */
    QNetworkInterface lIf (QNetworkInterface::interfaceFromName (cAdapterName));
    if (lOldFlags != lIf.flags ())                 /* ... if there has been any change in the interface status ... */
    {
       lOldFlags = lIf.flags ();
       if (lIf.flags () & 0x02)                      /* ... if the interface is running ... */
       {
           cSocket.disconnectFromHost ();
           #if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
           if (!cSocket.bind (QHostAddress ("0.0.0.0"), 65000, QUdpSocket::ReuseAddressHint))
           #else
           if (!cSocket.bind (QHostAddress ("0.0.0.0"), 65000, QUdpSocket::ShareAddress))            
           #endif
             lOldFlags = 0;
           else
           {
             int lTTL = 1;
             ip_mreq lMReq;
             memset ((void *) &lMReq, 0, sizeof (lMReq));
             lMReq.imr_multiaddr.s_addr = _HTONL (QHostAddress ("239.0.0.104").toIPv4Address ());
             lMReq.imr_interface.s_addr = _HTONL (QHostAddress ("0.0.0.0").toIPv4Address ());
             if (setsockopt (cSocket.socketDescriptor (), IPPROTO_IP, IP_ADD_MEMBERSHIP, (const char *) &lMReq, sizeof (lMReq)) < 0) lOldFlags = 0;
             if (setsockopt (cSocket.socketDescriptor (), IPPROTO_IP, IP_MULTICAST_TTL, (const char *) &lTTL, sizeof (lTTL)) < 0)  lOldFlags = 0;
           }
       }
    }
    

    /*
    ** If there are the conditions write a datagram ...
    */
    /* ... some code here to detect the conditions ... */
   cSocket.writeDatagram (lMsg.data (), lMsg.size (), QHostAddress ("239.0.0.104"), 65000);

} /* end forevere loop */

To copy to clipboard, switch view to plain text mode