sockaddr;
socklen_t addrlen;
struct ip_mreq mreq;
int nrecv;
char buf[MAX_LINE];...= AF_INET;
//sockaddr.sin_port = htons(SERVER_PORT);
if(inet_pton(AF_INET, argv[1], &sockaddr.sin_addr...sockaddr*)&sockaddr, addrlen);//接收套接字绑定多播地址
mreq.imr_multiaddr = sockaddr.sin_addr;
//inet_pton...*)&sockaddr, &addrlen);
printf("from %s: %s\n",
inet_ntop(AF_INET, &...sendto(sendfd, "test data", strlen("test data")+1, 0, (struct sockaddr*)&sockaddr, addrlen