代码

structip_mreq
{
     struct in_addr imr_multiaddr;
     struct in_addr imr_interface;
};

struct  ip_mreq mreq;
bzero(&mreq, sizeof(mreq));
mreq.imr_multiaddr.s_addr = inet_addr(“235.10.10.3”);
mreq.imr_interface.s_addr = htonl(INADDR_ANY);
setsockopt(sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,sizeof(mreq));