udprec.c

linux下UDP消息发送及接收 在UBUNTU 8.10下测试通过

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define BUFLEN 255

int 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) {
		printf("socket creating err in udptalk\n");
		exit(1);
	}

	/* 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);
	/* 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(-1);
	}

	/**重要：共享UDP组播端口**/
	int one = 1;
	setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
	/****/

	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(7838);

	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);
	}

	/* 绑定自己的端口和IP信息到socket上 */
	if (bind(sockfd, (struct sockaddr *) &peeraddr,sizeof(struct sockaddr_in)) == -1) {
		printf("Bind error\n");
		exit(0);
	}

	/* 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 err in udptalk!\n");
			exit(4);
		} else {
			/* 成功接收到数据报 */
			recmsg[n] = 0;
			printf("peer:%s\n", recmsg);
			/* 判断退出 */
			if (strcmp(recmsg,"exit\n")==0)  {
				close(sockfd);
				exit(1);
			}
		}
	}
}