Linux之UDP组播示例——双向通信

最新推荐文章于 2025-05-18 00:08:37 发布

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本文详细介绍了基于UDP的组播通信模型，包括如何在客户端加入组播组、发送和接收组播消息的过程。通过两个示例程序a.c和b.c展示了组播通信的实现细节，以及如何在局域网内进行组播通信。

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//a.c 先发数据后等待接收，b.c 先等待接收数据后发送数据

// a.c

#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

int main (int argc, char **argv)
{
    struct sockaddr_in peeraddr,ia;
    int sockfd;
    unsigned char loop;
    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);
    }
   loop = 0; 
   if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_LOOP, &loop,sizeof (loop)) == -1)
   {
       printf("IP_MULTICAST_LOOP set fail!\n");
   }
 
    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 (;;)
    {
        printf("Please input:\n");
        bzero (recmsg, BUFLEN + 1);
        if (fgets (recmsg, BUFLEN, stdin) == (char *) EOF)
            exit (0);

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

        printf ("send ok\n");
        bzero (recmsg, BUFLEN + 1);
        n = recvfrom (sockfd, recmsg, BUFLEN, 0, (struct sockaddr *) &ia, &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 ("recv:[%s]\n", recmsg);
        }
    }
}

//b.c

#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


int main (int argc, char **argv)
{
  struct sockaddr_in peeraddr,ia;
  int sockfd;
    unsigned char loop;
  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);
  }
     loop = 0;
     if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_LOOP, &loop,sizeof (loop)) == -1)
     {
        printf("IP_MULTICAST_LOOP set fail!\n");
     }

   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 *) &ia, &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 ("recv:[%s]\n", recmsg);
    }

        printf("Please input:\n");
    bzero (recmsg, BUFLEN + 1);
    if (fgets (recmsg, BUFLEN, stdin) == (char *) EOF)
      exit (0);
        //只向对方回复数据，不向组内其他成员发送数据
        //if (sendto(sockfd, recmsg, strlen (recmsg), 0, (struct sockaddr *) &ia, sizeof ( ia)) < 0)
        //向组内所有成员发送数据，除了自己
        if (sendto(sockfd, recmsg, strlen (recmsg), 0, (struct sockaddr *) &peeraddr, sizeof ( peeraddr)) < 0)
    {
      printf ("sendto error!\n");
      exit (3);
    }
    printf ("send ok\n");
  }
}

编译：

gcc a.c -o a

gcc b.c -o b

运行程序：同一局域网内在两台不同的主机上分别运行上述可执行程序a、b:

./a ./b