Using the same port for 2 UDP Multicast groups

I habe a program, that can send and receive UDP Multicast telegrams. When I open the socket then I bind my multicast group address and the local port to a specified networkcard (our PC has 2 network cards). Now I have a special constellation:

Our PC has 2 network cards. Multicast group 1 shall use card 1 and group shall use card 2. As long as both groups use different local ports it works fine. But when both group want to use the same port number then I can receive and send telegrams only through the first group that was created. For the second one I don't even get a FD_READ event at all.

Code:

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      SrvAddr.sin_family        = AF_INET;
      SrvAddr.sin_port          = htons( (WORD) nLocalPort );
     
      SrvAddr.sin_addr.s_addr    = inet_addr(strOwnIpAddress); // bind multicast group socket to a specified networkcard
     
      // If bind socket to port failed
      if( bind( hSocket,
                      (const struct sockaddr *) &SrvAddr,
                      sizeof(SrvAddr) )              == SOCKET_ERROR )
      {
            WSACloseEvent(ptChannel->Overlapped.hEvent);
            closesocket(hSocket);
            WSACleanup();
            return ceUdpErrBind;
      }  // END OF If bind socket to port failed

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I found my mistake. Problem is solved

Quote:

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Originally Posted by grka

I found my mistake. Problem is solved

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Will you be so kind to share your solution?