title: Receiving multicast data from different groups on the same socket in linux
body: <p>Say I want to receive data from 239.1.2.3:20000 and also from 239.4.5.6:20001 in a linux C program. Can I do so with just one socket?  </p>
  
  <p>I can of course join multiple groups on the socket using the IP_ADD_MEMBERSHIP <code>setsockopt</code> option, but, since the ports are different, I am not sure if it is possible to somehow "bind to both ports"</p>