#include <sys/types.h>#include <sys/socket.h>#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#define BUFLEN 255int main(int argc, char **argv){	struct sockaddr_in peeraddr, myaddr;	int sockfd;	char recmsg[BUFLEN + 1];	unsigned int socklen;	/* 創(chuàng)建 socket 用于UDP通訊 */	sockfd = socket(AF_INET, SOCK_DGRAM, 0);	if (sockfd < 0) {		printf("socket creating error\n");		exit(1);	}	socklen = sizeof(struct sockaddr_in);	/* 設置對方的端口和IP信息 */	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]) {		/* 注意這里設置的對方地址是指組播地址，而不是對方的實際IP地址 */		if (inet_pton(AF_INET, argv[1], &peeraddr.sin_addr) <= 0) {			printf("wrong group address!\n");			exit(0);		}	} else {		printf("no group address!\n");		exit(0);	}	/* 設置自己的端口和IP信息 */	memset(&myaddr, 0, socklen);	myaddr.sin_family = AF_INET;	if (argv[4]) myaddr.sin_port = htons(atoi(argv[4]));	else myaddr.sin_port = htons(23456);	if (argv[3]) {		if (inet_pton(AF_INET, argv[3], &myaddr.sin_addr) <= 0) {			printf("self ip address error!\n");			exit(0);		}	} else myaddr.sin_addr.s_addr = INADDR_ANY;	/* 綁定自己的端口和IP信息到socket上 */	if (bind(sockfd, (struct sockaddr *) &myaddr,sizeof(struct sockaddr_in)) == -1) {		printf("Bind error\n");		exit(0);	}	/* 循環(huán)接受用戶輸入的消息發(fā)送組播消息 */	for (;;) {	/* 接受用戶輸入 */		bzero(recmsg, BUFLEN + 1);		if (fgets(recmsg, BUFLEN, stdin) == (char *) EOF) exit(0);		/* 發(fā)送消息 */		if (sendto(sockfd, recmsg, strlen(recmsg), 0,(struct sockaddr *) &peeraddr,sizeof(struct sockaddr_in)) < 0) {			printf("sendto error!\n");			exit(3);		}		printf("...... send ok\n");		/* 判斷退出 */		if (strcmp(recmsg,"exit\n")==0)  {			close(sockfd);			exit(1);		}	}}