#include #include #include #include #include #include #include #define HELLO_PORT 50004 #define HELLO_GROUP "239.255.0.0" #define MSGBUFSIZE 1416 struct sockaddr_in addr; int fd; void setup_rsocket_(void) { struct ip_mreq mreq; u_int yes=1; /* create what looks like an ordinary UDP socket */ if ((fd=socket(AF_INET,SOCK_DGRAM,0)) < 0) { perror("socket"); exit(1); } /* allow multiple sockets to use the same PORT number */ if (setsockopt(fd,SOL_SOCKET,SO_REUSEADDR,&yes,sizeof(yes)) < 0) { perror("Reusing ADDR failed"); exit(1); } /* set up destination address */ memset(&addr,0,sizeof(addr)); addr.sin_family=AF_INET; addr.sin_addr.s_addr=htonl(INADDR_ANY); /* N.B.: differs from sender */ addr.sin_port=htons(HELLO_PORT); /* bind to receive address */ if (bind(fd,(struct sockaddr *) &addr,sizeof(addr)) < 0) { perror("bind"); exit(1); } /* use setsockopt() to request that the kernel join a multicast group */ mreq.imr_multiaddr.s_addr=inet_addr(HELLO_GROUP); mreq.imr_interface.s_addr=htonl(INADDR_ANY); if (setsockopt(fd,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq)) < 0) { perror("setsockopt"); exit(1); } } void recv_pkt_(char buf[]) { int addrlen,nbytes; addrlen=sizeof(addr); if ((nbytes=recvfrom(fd,buf,1416,0, (struct sockaddr *) &addr,&addrlen)) < 0) { perror("recvfrom"); exit(1); } }