广播是在局域网之间的一对多的通信方式，使用的udp协议
/*** client.c ***/ #include <stdio.h> #include <unistd.h> #include <string.h> #include <sys/socket.h> #include <arpa/inet.h> #define SERVER_PORT 8000 #define MAXLINE 4096 #define CLIENT_PORT 9000 int main(int argc, char *argv[]) { struct sockaddr_in localaddr; int confd; ssize_t len; char buf[MAXLINE]; //1.创建一个socket confd = socket(AF_INET, SOCK_DGRAM, 0); //2.初始化本地端地址 bzero(&localaddr, sizeof(localaddr)); localaddr.sin_family = AF_INET; inet_pton(AF_INET, "0.0.0.0" , &localaddr.sin_addr.s_addr); localaddr.sin_port = htons(CLIENT_PORT); int ret = bind(confd, (struct sockaddr *)&localaddr, sizeof(localaddr)); //显示绑定不能省略 if (ret == 0) printf("...bind ok...\n"); while (1) { len = recvfrom(confd, buf, sizeof(buf), 0, NULL, 0); write(STDOUT_FILENO, buf, len); } close(confd); return 0; } /*** server.c ***/ #include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/socket.h> #include <string.h> #include <arpa/inet.h> #include <net/if.h> #define SERVER_PORT 8000 /* 无关紧要 */ #define MAXLINE 1500 #define BROADCAST_IP "192.168.42.255" #define CLIENT_PORT 9000 /* 重要 */ int main(void) { int sockfd; struct sockaddr_in serveraddr, clientaddr; char buf[MAXLINE]; /* 构造用于UDP通信的套接字 */ sockfd = socket(AF_INET, SOCK_DGRAM, 0); bzero(&serveraddr, sizeof(serveraddr)); serveraddr.sin_family = AF_INET; /* IPv4 */ serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); /* 本地任意IP INADDR_ANY = 0 */ serveraddr.sin_port = htons(SERVER_PORT); bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)); int flag = 1; setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &flag, sizeof(flag)); /*构造 client 地址 IP+端口 192.168.7.255+9000 */ bzero(&clientaddr, sizeof(clientaddr)); clientaddr.sin_family = AF_INET; inet_pton(AF_INET, BROADCAST_IP, &clientaddr.sin_addr.s_addr); clientaddr.sin_port = htons(CLIENT_PORT); int i = 0; while (1) { sprintf(buf, "Drink %d glasses of water\n", i++); //fgets(buf, sizeof(buf), stdin); sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&clientaddr, sizeof(clientaddr)); sleep(1); } close(sockfd); return 0; } 来源：博客园
作者：王清河
链接：https://www.cnblogs.com/wanghao-boke/p/11443724.html