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

#define BUFLEN 255

intmain (int argc, char **argv) {  struct sockaddr_in peeraddr,ia;  int sockfd; char recmsg[BUFLEN + 1];     unsigned int socklen, n; 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)); 

    inet_pton(AF_INET,"224.0.1.2",&ia.sin_addr);/* 设置组地址 */     bcopy (&ia.sin_addr.s_addr, &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);       }

    socklen = sizeof (struct sockaddr_in);     memset (&peeraddr, 0, socklen);     peeraddr.sin_family = AF_INET;    peeraddr.sin_port = htons (7838);    inet_pton(AF_INET, "224.0.1.2", &peeraddr.sin_addr); 

/* 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", recmsg);            }

    }

}

#include <sys/types.h>#include <sys/socket.h>#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <string.h>

#define BUFLEN 255

int main (int argc, char **argv) {

struct sockaddr_in peeraddr, myaddr; int sockfd;  char recmsg[BUFLEN + 1];    unsigned int socklen;    socklen = sizeof (struct sockaddr_in);  

/* 创建 socket 用于UDP通讯 */     sockfd = socket (AF_INET, SOCK_DGRAM, 0);if (sockfd < 0)    {              printf ("socket creating error\n");             exit (1);       }  

/* 设置对方的端口和IP信息 */     memset (&peeraddr, 0, socklen);     peeraddr.sin_family = AF_INET;      peeraddr.sin_port = htons (7838);    inet_pton (AF_INET, "224.0.1.2", &peeraddr.sin_addr);

/* 设置自己的端口和IP信息 */     memset (&myaddr, 0, socklen);     myaddr.sin_family = AF_INET;     myaddr.sin_port = htons (23456);     myaddr.sin_addr.s_addr = INADDR_ANY;

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

/* 循环接受用户输入的消息发送组播消息 */ for (;;)    {      /* 接受用户输入 */         bzero (recmsg, BUFLEN + 1);     if (fgets (recmsg, BUFLEN, stdin) == (char *) EOF)                exit (0);

/* 发送消息 */ if (sendto(sockfd, recmsg, strlen (recmsg), 0, (struct sockaddr *) &peeraddr, sizeof (struct sockaddr_in)) < 0)        {                  printf ("sendto error!\n");                  exit (3);            }

        printf ("'%s' send ok\n", recmsg);    } }