下面程序实现了多播发送与接收:
news_sender.c
//多播:向多播组中多个主机传递数据,多播组是D类IP地址 //多播方式是基于UDP完成的 //TTL:生存时间(数据包传递距离)。每经过一个路由器就减1,TTL变0时,数据包无法传递,只能销毁。 //广播:向同一网络中的主机传送数据。 //广播设置方法: //int bcast=1; //setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (void*)&bcast, sizeof(bcast)); #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <sys/socket.h> #define TTL 64 #define BUF_SIZE 30 void error_handling(char *message); int main(int argc, char *argv[]) { int sock; struct sockaddr_in mul_addr; socklen_t adr_sz; int str_len; char buf[BUF_SIZE]; int time_live=TTL; FILE *fp; if(argc!=3) { exit(1); } sock=socket(PF_INET, SOCK_DGRAM, 0); if(sock == -1) error_handling("socket error!"); //配置地址 memset(&mul_addr, 0, sizeof(mul_addr)); mul_addr.sin_family = AF_INET; mul_addr.sin_addr.s_addr = inet_addr(argv[1]); mul_addr.sin_port = htons(atoi(argv[2])); //设置TTL setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, (void*)&time_live, sizeof(time_live)); if((fp=fopen("news.txt", "r"))==NULL) error_handling("fopen error"); while(!feof(fp)) { fgets(buf, BUF_SIZE, fp); //向mul_addr发送多播数据 sendto(sock, buf, strlen(buf), 0, (struct sockaddr*)&mul_addr, sizeof(mul_addr)); sleep(2); } fclose(fp); close(sock); return 0; } void error_handling(char *message) { fputs(message, stderr); fputc('\n', stderr); exit(1); }
news_receiver.c
//多播接收程序,需要有加入多播组的过程,剩下的和UDP差不多 #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <sys/socket.h> #include <boost/concept_check.hpp> #define BUF_SIZE 30 void error_handling(char *message); int main(int argc, char *argv[]) { int recv_sock; struct sockaddr_in addr; struct sockaddr_in clnt_addr; socklen_t clnt_addr_size; int str_len; char buf[BUF_SIZE]; struct ip_mreq join_adr; if(argc!=2) { exit(1); } //1.创建UDP套接字 recv_sock=socket(PF_INET, SOCK_DGRAM, 0); if(recv_sock == -1) error_handling("socket error!"); //2.配置地址 memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; //IPV4协议族 addr.sin_addr.s_addr = htonl(INADDR_ANY); //主机字节序(host)转换成网络字节序(net)(大端序) addr.sin_port = htons(atoi(argv[2])); if(bind(recv_sock, (struct sockaddr*) &addr, sizeof(addr)) == -1) error_handling("bind error"); //将当前主机加入多播组:初始化多播组地址,初始化待加入主机的IP地址 join_adr.imr_multiaddr.s_addr=inet_addr(argv[1]); join_adr.imr_interface.s_addr=htonl(INADDR_ANY); setsockopt(recv_sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (void*)&join_adr, sizeof(join_adr)); while(1) { //接收多播数据,最后两个参数设置为NULL和0就行 str_len=recvfrom(recv_sock, buf, BUF_SIZE-1, 0, NULL, 0); if(str_len<0) break; buf[str_len]=0; fputs(buf, stdout); } close(recv_sock); return 0; } void error_handling(char *message) { fputs(message, stderr); fputc('\n', stderr); exit(1); }