组播练习

host.c：

#include
#include
#include
#include
#include
#include
#include
#include
#include

int main(int argc, char **argv)
{
    struct sockaddr_in peeraddr;
    struct in_addr ia;
    int sockfd;
    char msg[100];
    unsigned socklen, n;
    struct hostent *group;
    struct ip_mreq mreq;
   
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
   
    bzero(&mreq, sizeof(struct ip_mreq));

    mreq.imr_multiaddr.s_addr = inet_addr("230.1.1.78");
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);
   
    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);
    peeraddr.sin_addr.s_addr = htonl(INADDR_ANY);
  
   
    if (bind (sockfd, (struct sockaddr *) &peeraddr, sizeof(struct sockaddr_in)) == -1) {
      printf("Bind error\n");
      exit(0);
    }
    bzero(msg, sizeof(msg));
    n = recvfrom(sockfd, msg, 100, 0,(struct sockaddr *) &peeraddr, &socklen);
    printf("host recv:%s(%d)\n", msg, n);
}

 

cli.c：

#include
#include
#include
#include
#include
#include

int main(int argc, char **argv)
{
  struct sockaddr_in peeraddr, myaddr;
 
  int sockfd;
  char msg[100]="i am toy";
  unsigned int socklen;
 
  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  socklen = sizeof(struct sockaddr_in);
 
  bzero(&peeraddr, socklen);
  peeraddr.sin_family = AF_INET;
  peeraddr.sin_port = htons(7838);
  peeraddr.sin_addr.s_addr = inet_addr("230.1.1.78");

  if (sendto(sockfd, msg, strlen(msg), 0,(struct sockaddr *) &peeraddr, socklen) < 0) {
      printf("sendto error!\n");
      exit(3);
  }
  printf("'%s' send ok\n", msg);
}

 makefile见其他udp程序。

 

 组播和广播，从发送端来看就是IP地址不同，广播是最后一个为255，而组播是在239.0.0.0～239.255.255.255范围内的IP。从性能来说，广播要求所有节点都接受和处理，如果不需要则舍弃；而组播可以使部分主机进行处理。而接收端相对广播多了上面红色部分。