networking question

Hey all, I have got a strange bug(?) while testing the multicasting server and client. I have done only the INADDR_ANY bind in server and client adds its IP_MULTICAST_IF to 224.0.0.1 , surprisingly i recvd pkts from the client with out joining using IP_ADD_MEMBERSHIP. Is that a bug? or as we listening on INADDR_ANY will make us recv all the mcast/bcast pkts? while if i do tx on 224.0.0.3 , the server is not able to recv the packets. any ideas?