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Is it possible to receive data from more than one multicast group on a single socket? For example: void AddGroup(int sock, const char* mc_addr_str, int mc_port, const char* interface) { struct sockaddr_in mc_addr; memset(&mc_addr, 0, sizeof(mc_addr)); mc_addr.sin_family = AF_INET; mc_addr.sin_addr.s_addr = inet_addr(mc_addr_str); mc_addr.sin_port = htons(mc_port); if ((bind(sock, (struct sockaddr *) &mc_addr, sizeof(mc_addr))) < 0) { perror("bind() failed"); exit(1); } // construct an IGMP join request structure struct ip_mreq mc_req; mc_req.imr_multiaddr.s_addr = inet_addr(mc_addr_str); mc_req.imr_interface.s_addr = inet_addr(interface); if ((setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*) &mc_req, sizeof(mc_req))) < 0) { perror("setsockopt() failed"); exit(1); } } This code works when I add one multicast group. But when I try to add another, the "bind" fails. I don't quite understand why the bind needs to be there in the first place? (but the code doesn't work without it). Ideally I would like to call AddGroup multiple times on the same socket. Is this possible? Or do I need one socket per group and then just use polling?

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