multiple multicast on multiple interfaces

I have done quite a bit of research on this but I can't find really any articles that's doing this exact setup I have. This is a pretty specific setup, so I am going to do my best to describe what I am doing and what I am trying to do.

I have a computer with 2 Ethernet ports (eth0 and eth1). Each one is receiving a different multicast broadcast at the same time. So 1 Multicast IP address and port is going to eth0 and another multicast IP address and port is going to eth1.

I am writing a program that is designed to listen to a given multicast IP address and port.

The goal is to be able to launch the program and listen to 1 of the multicast and at the same time launch a 2nd instance of the program that listens to the other multicast. The program itself is only designed to listen to 1 multicast at a time.

However I can not seem to have both programs running at the same time.

Using the "route" command I have been able to set up the routing table where I can receive 1 of the streams, but not the other. I can only ever get 1 stream going at a time, but not both.

eth0 is connected to: 10.10.20.50 -- multicast for this interface is 225.0.7.10 port 51007 eth1 is connected to: 192.168.20.21 -- multicast for this interface is 225.0.8.10 port 51008

If I do the route command, "route add default gw 10.10.20.50 eth0" I can receive the multicast on that address just fine

But as soon as I add "route add default gw 192.168.20.21 eth1" I can no longer receive the multicast on the 10.10.20.50 interface.

I do not get any errors with binding the sockets or setting the sockopts... the program just simply blocks on the recv call and never gets a message.

I have tried all sorts of combinations of the route command to support this, and I have done some various things in my connection code to fix this as well but with no luck. Here is my current connection code:

  //Create the UDP socket, check to make sure it was created successfully
  cout << "Initializing Connection..." << endl ;
  m_socket = socket ( AF_INET , SOCK_DGRAM , IPPROTO_UDP ) ;

  if( m_socket == -1 )
  {
    cout << "ERROR CREATING SOCKET: " << strerror(errno) << endl ;
    return false ;
  }

  cout << "Socket Created" << endl;

  //Setup socket binding information
  sockaddr_in addr ;
  bzero  ( ( char* ) &addr , sizeof ( addr ) ) ;
  addr . sin_family       = AF_INET ;
  addr . sin_addr.s_addr  = inet_addr(interface_addr) ; //10.10.20.50 or 192.168.20.21
  addr . sin_port         = htons ( port ) ;            //51007 or 51008

  //bind the socket, check for errors
  int result = bind ( m_socket , ( struct sockaddr* ) &addr , sizeof ( addr ) ) ;

  if ( result == -1 )
  {
    cout << "ERROR BINDING PORT: " << strerror ( errno ) << endl;
    shutdown ( m_socket , SHUT_RDWR ) ;
    return false ;
  }

  cout << "Socket Bound" << endl;

  //subscribe to the supplied IP address and port to listen on
  in_addr host_addr ;
  inet_pton ( AF_INET , ip_addrs . c_str () , & ( host_addr ) ) ;

  struct ip_mreq mreq;
  mreq . imr_multiaddr = host_addr ;       // multicast address 225.0.7.10 or 225.0.8.10
  mreq . imr_interface = addr . sin_addr ; //the 10.10.20.50 or 192.168.20.21 specified above

  result = setsockopt ( m_socket , IPPROTO_IP , IP_ADD_MEMBERSHIP, &mreq , sizeof(mreq) ) ;

  if ( result == -1 )
  {
    cout << "ERROR SETTING SOCKOPT SUBSCRIPTION: " << strerror(errno) << endl ;
    printSocketError();
    shutdown ( m_socket , SHUT_RDWR ) ;
    return false ;
  }

  /*
   * Read from the socket to get the initial bit of information we need so the
   * buffers can get allocated correctly, and the width and height of the application
   * can be defined.
   */
  cout << "Attempting to read from the socket..." << endl;
  MyPacket pckt ;
  recv ( m_socket , &pckt , sizeof ( pckt ) , MSG_PEEK ) ;

  cout << "Data Received... processing" << endl ;

I have also tried using the ip_mreqn struct to specify the interface manually and used the setsockopt for SOL_BINDTODEVICE setup (eth0 or eth1) but ran into the same problem as before where I could only get it to connect if I had a particular route setup... and even then only 1 would receive and not the other.

To reiterate... I need to have 2 copies of this program running at the same time.. each one listening to it's own specified multicast address coming from specific interfaces.