11.3.6 一个多播例子的客户端

11.3.6  一个多播例子的客户端

多播组的IP地址为224.0.0.88，端口为8888，当客户端接收到多播的数据后将打印         出来。

客户端只有在加入多播组后才能接受多播组的数据，因此多播客户端在接收多播组的数据之前需要先加入多播组，当接收完毕后要退出多播组。

 

/*

*broadcast_client.c - 多播的客户端

*/

#define MCAST_PORT 8888;

#define MCAST_ADDR "224.0.0.88"     /*一个局部连接多播地址，路由器不进行转发*/

#define MCAST_INTERVAL 5                        /*发送间隔时间*/

#define BUFF_SIZE 256                           /*接收缓冲区大小*/

int main(int argc, char*argv[])

{  

    int s;                                      /*套接字文件描述符*/

    struct sockaddr_in local_addr;              /*本地地址*/

    int err = -1;

   

    s = socket(AF_INET, SOCK_DGRAM, 0);     /*建立套接字*/

    if (s == -1)

    {

        perror("socket()");

        return -1;

    }  

   

                                                /*初始化地址*/

    memset(&local_addr, 0, sizeof(local_addr));

    local_addr.sin_family = AF_INET;

    local_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    local_addr.sin_port = htons(MCAST_PORT);

   

                                                /*绑定socket*/

    err = bind(s,(struct sockaddr*)&local_addr, sizeof(local_addr)) ;

    if(err < 0)

    {

        perror("bind()");

        return -2;

    }

   

                                                /*设置回环许可*/

    int loop = 1;

    err = setsockopt(s,IPPROTO_IP, IP_MULTICAST_LOOP,&loop, sizeof(loop));

    if(err < 0)

    {

        perror("setsockopt():IP_MULTICAST_LOOP");

        return -3;

    }

   

    struct ip_mreq mreq;                                    /*加入广播组*/

    mreq.imr_multiaddr.s_addr = inet_addr(MCAST_ADDR); /*广播地址*/

    mreq.imr_interface.s_addr = htonl(INADDR_ANY); /*网络接口为默认*/

                                                        /*将本机加入广播组*/

    err = setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof
    (mreq));

    if (err < 0)

    {

        perror("setsockopt():IP_ADD_MEMBERSHIP");

        return -4;

    }

   

    int times = 0;

    int addr_len = 0;

    char buff[BUFF_SIZE];

    int n = 0;

                                        /*循环接收广播组的消息，5次后退出*/

    for(times = 0;times<5;times++)

    {

        addr_len = sizeof(local_addr);

        memset(buff, 0, BUFF_SIZE);                 /*清空接收缓冲区*/

                                                    /*接收数据*/

        n = recvfrom(s, buff, BUFF_SIZE, 0,(struct sockaddr*)&local_addr,
        &addr_len);

        if( n== -1)

        {

            perror("recvfrom()");

        }

                                                    /*打印信息*/

        printf("Recv %dst message from server:%s/n", times, buff);

        sleep(MCAST_INTERVAL);

    }

   

                                                    /*退出广播组*/

    err = setsockopt(s, IPPROTO_IP, IP_DROP_MEMBERSHIP,&mreq, sizeof
    (mreq));

       

    close(s);

    return 0;

}