Generally Multicast Sockets should be bound to the wildcard address [INADDR_ANY], before joining the group. Once the binding is done, you can join to the desired group by calling SetSockOpt API with IP_ADD_MEMBERSHIP providing the IP address of the desired interface and the ip address of the multicast...

   IP Datagrams gets routed dynamically in the sense, we cannot precisely predict which path every IP Datagram will take to reach the destination. Some times you may need to fix the path[ a set of routers] through which the IP Datagram must travel to reach the destination. IP Source Routing...

Possible Scenario: On Windows XP or Windows Server 2003 by default IGMPv3 is enabled. When you send a IGMP multicast packet after joining the multicast group using IP_ADD_SOURCE_MEMBERSHIP and setsockopt(), you see that IGMPv2 packet is going out of the machine, while you are expecting IGMPv3 to go out...