广播是某一个终端给一个子网发送数据,这个子网可以是本地的最小化子网,比如 192.168.1.255,也可以是整个子网 255.255.255.255,这取决于你要发送的范围,本文中只介绍一个最小化的广播程序,值得注意的是,即使客户端没有设定IP地址,它依然是可以接收到广播数据的。
服务端代码
#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/socket.h> #include <string.h> #include <unistd.h> #include <arpa/inet.h> #include <net/if.h> #define SERVER_PORT 8000 #define CLIENT_PORT 9000 #define MAXLINE 1500 #define BROADCAST_IP "255.255.255.255" // 广播地址 int main(void) { int sockfd; struct sockaddr_in serveraddr, clientaddr; char buf[MAXLINE] = "mycode\n"; /* 构造用于UDP通信的套接字 */ sockfd = socket(AF_INET, SOCK_DGRAM, 0); bzero(&serveraddr, sizeof(serveraddr)); /* IPv4 */ serveraddr.sin_family = AF_INET; /* 本地任意IP INADDR_ANY = 0 */ serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); serveraddr.sin_port = htons(SERVER_PORT); bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)); // 设置socket为广播方式 int flag = 1; setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &flag, sizeof(flag)); /*构造 client 地址 IP+端口 192.168.12.255+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, "mycode %d\n", i++); // 发送数据 sendto(sockfd, buf, strlen(buf), 0, (struct sockaddr *)&clientaddr, sizeof(clientaddr)); sleep(1); } close(sockfd); return 0; }
客户端代码
#include <netinet/in.h> #include <stdio.h> #include <sys/types.h> #include <sys/socket.h> #include <arpa/inet.h> #include <string.h> #include <stdlib.h> #include <sys/stat.h> #include <unistd.h> #include <fcntl.h> #include <net/if.h> #define SERVER_PORT 8000 #define MAXLINE 4096 #define CLIENT_PORT 9000 int main(int argc, char *argv[]) { struct sockaddr_in serveraddr, 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); // 广播客户端也要绑定固定的端口,否则接收不到 bind(confd, (struct sockaddr *)&localaddr, sizeof(localaddr)); socklen_t slen; while (1) { slen = sizeof(serveraddr); len = recvfrom(confd, buf, sizeof(buf), 0, (struct sockaddr *)&serveraddr, &slen); //printf("%s\n", inet_ntop(AF_INET, &serveraddr.sin_addr.s_addr, buf, sizeof(buf))); write(STDOUT_FILENO, buf, len); } close(confd); return 0; }
编译
编译客户端:gcc boardcast_client.c -o boardcast_client
编译服务端:gcc boardcast_server.c -o boardcast_server
运行效果: