客户端源码：
#include#include #include #include #include #include #include #define BUFLEN 255int main(int argc, char **argv){ struct sockaddr_in peeraddr; int sockfd; char recmsg[BUFLEN + 1]; unsigned int socklen; /* 创建 socket 用于UDP通讯 */ sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd < 0) { perror("socket\n"); exit(errno); } printf("socket created success!!!\n"); socklen = sizeof(struct sockaddr_in); /* 设置对方的端口和IP信息 */ memset(&peeraddr, 0, socklen); peeraddr.sin_family = AF_INET; if (argv[2]) peeraddr.sin_port = htons(atoi(argv[2])); else peeraddr.sin_port = htons(4567); if (argv[1]) { /* 注意这里设置的对方地址是指组播地址，而不是对方的实际IP地址 */ if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0) { printf("wrong group address!\n"); exit(0); } } else { printf("no group address!\n"); exit(0); } /* 循环接受用户输入的消息发送组播消息 */ for (;;) { /* 接受用户输入 */ bzero(recmsg, BUFLEN + 1); if (fgets(recmsg, BUFLEN, stdin) == (char *)EOF) exit(0); /* 发送消息 */ if (sendto (sockfd, recmsg, strlen(recmsg), 0, (struct sockaddr *)&peeraddr, sizeof(struct sockaddr_in)) < 0) { printf("sendto error!\n"); exit(errno); } printf("client sendto success!\n"); } return 0;}
服务端源码：
#include#include #include #include #include #include #include #include #define BUFLEN 255int main(int argc, char **argv){ struct sockaddr_in peeraddr; struct in_addr ia; int sockfd; char recmsg[BUFLEN + 1]; unsigned int socklen, n; struct hostent *group; struct ip_mreq mreq; /* 创建 socket 用于UDP通讯 */ sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd < 0) { perror("socket\n"); exit(errno); } printf("socket created success!!!\n"); /* 设置要加入组播的地址 */ bzero(&mreq, sizeof(struct ip_mreq)); if (argv[1]) { if ((group = gethostbyname(argv[1])) == (struct hostent *)0) { perror("gethostbyname"); exit(errno); } } else { printf ("you should give me a group address, 224.0.0.0-239.255.255.255\n"); exit(errno); } bcopy((void *)group->h_addr, (void *)&ia, group->h_length); printf("组播地址：%s\n", inet_ntoa(ia)); /* 设置组地址 */ bcopy(&ia, &mreq.imr_multiaddr.s_addr, sizeof(struct in_addr)); /* 设置发送组播消息的源主机的地址信息 */ mreq.imr_interface.s_addr = htonl(INADDR_ANY); /* 把本机加入组播地址，即本机网卡作为组播成员，只有加入组才能收到组播消息 */ if (setsockopt (sockfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(struct ip_mreq)) == -1) { perror("setsockopt"); exit(errno); } socklen = sizeof(struct sockaddr_in); memset(&peeraddr, 0, socklen); peeraddr.sin_family = AF_INET; if (argv[2]) peeraddr.sin_port = htons(atoi(argv[2])); else peeraddr.sin_port = htons(4567); if (argv[1]) { if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0) { printf("Wrong dest IP address!\n"); exit(0); } } else { printf("no group address given, 224.0.0.0-239.255.255.255\n"); exit(errno); } /* 绑定组播地址的端口和IP信息到socket上 */ if (bind (sockfd, (struct sockaddr *)&peeraddr, sizeof(struct sockaddr_in)) == -1) { printf("Binded failure\n"); exit(0); } else printf("binded success!!!\n"); /* 循环接收网络上来的组播消息 */ for (;;) { bzero(recmsg, BUFLEN + 1); n = recvfrom(sockfd, recmsg, BUFLEN, 0, (struct sockaddr *)&peeraddr, &socklen); if (n < 0) { printf("recvfrom error in udptalk!\n"); exit(errno); } else { /* 成功接收到数据报 */ recmsg[n] = 0; printf("peer info:%s", recmsg); } } return 0;}
编译：
$ gcc -o client client.c$ gcc -o server server.c
运行参考样例：
$ ./client 234.1.2.3 4567socket created success!!!just to test!client sendto success!$ ./server 234.1.2.3 4567socket created success!!!组播地址：234.1.2.3binded success!!!peer info:just to test!