linux网络编程之广播详细代码及文档说明

/********************************************************************* * Filename: bcast_client.c * Description:广播客户端代码 * Author: Eric(wongpz@foxmail.com) * Date: 2012-9-14 ********************************************************************/ #include<stdio.h> #include<stdlib.h> #include<unistd.h> #include<string.h> #include<sys/socket.h> #include<arpa/inet.h> #include<netinet/in.h> #include<sys/types.h> #include<netdb.h> #include <sys/ioctl.h> #include <net/if.h> #define IP_FOUND "IP_FOUND" #define IP_FOUND_ACK "IP_FOUND_ACK" #define IFNAME "eth0" #define MCAST_PORT 9999 int main(int argc, char*argv[]) { int ret = -1; int sock = -1; int j = -1; int so_broadcast = 1; struct ifreq *ifr; struct ifconf ifc; struct sockaddr_in broadcast_addr; //广播地址 struct sockaddr_in from_addr; //服务端地址 int from_len = sizeof(from_addr); int count = -1; fd_set readfd; //读文件描述符集合 char buffer[1024]; struct timeval timeout; timeout.tv_sec = 2; //超时时间为2秒 timeout.tv_usec = 0; //建立数据报套接字 sock = socket(AF_INET, SOCK_DGRAM, 0); if (sock < 0) { perror("create socket failed:"); return -1; } // 获取所有套接字接口 ifc.ifc_len = sizeof(buffer); ifc.ifc_buf = buffer; if (ioctl(sock, SIOCGIFCONF, (char *) &ifc) < 0) { perror("ioctl-conf:"); return -1; } ifr = ifc.ifc_req; for (j = ifc.ifc_len / sizeof(struct ifreq); --j >= 0; ifr++) { if (!strcmp(ifr->ifr_name, "eth0")) { if (ioctl(sock, SIOCGIFFLAGS, (char *) ifr) < 0) { perror("ioctl-get flag failed:"); } break; } } //将使用的网络接口名字复制到ifr.ifr_name中，由于不同的网卡接口的广播地址是不一样的，因此指定网卡接口 //strncpy(ifr.ifr_name, IFNAME, strlen(IFNAME)); //发送命令，获得网络接口的广播地址 if (ioctl(sock, SIOCGIFBRDADDR, ifr) == -1) { perror("ioctl error"); return -1; } //将获得的广播地址复制到broadcast_addr memcpy(&broadcast_addr, (char *)&ifr->ifr_broadaddr, sizeof(struct sockaddr_in)); //设置广播端口号 printf("\nBroadcast-IP: %s\n", inet_ntoa(broadcast_addr.sin_addr)); broadcast_addr.sin_family = AF_INET; broadcast_addr.sin_port = htons(MCAST_PORT); //默认的套接字描述符sock是不支持广播，必须设置套接字描述符以支持广播 ret = setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &so_broadcast, sizeof(so_broadcast)); //发送多次广播，看网络上是否有服务器存在 int times = 10; int i = 0; for (i = 0; i < times; i++) { //一共发送10次广播，每次等待2秒是否有回应 //广播发送服务器地址请求 timeout.tv_sec = 2; //超时时间为2秒 timeout.tv_usec = 0; ret = sendto(sock, IP_FOUND, strlen(IP_FOUND), 0, (struct sockaddr*) &broadcast_addr, sizeof(broadcast_addr)); if (ret < 0) { continue; } //文件描述符清0 FD_ZERO(&readfd); //将套接字文件描述符加入到文件描述符集合中 FD_SET(sock, &readfd); //select侦听是否有数据到来 ret = select(sock + 1, &readfd, NULL, NULL, &timeout); switch (ret) { case -1: break; case 0: perror("select timeout\n"); break; default: //接收到数据 if (FD_ISSET(sock,&readfd)) { count = recvfrom(sock, buffer, 1024, 0, (struct sockaddr*) &from_addr, &from_len); //from_addr为服务器端地址 printf("\trecvmsg is %s\n", buffer); if (strstr(buffer, IP_FOUND_ACK)) { printf("\tfound server IP is %s, Port is %d\n", inet_ntoa(from_addr.sin_addr), htons(from_addr.sin_port)); } return -1; } break; } } return 0; }