Linux网络编程--多播

int nTtl = 0; setsockopt(sock,IPPROTO_IP,IP_MULTICAST_TTL,(char*)&nTtl,sizeof(nTtl));

unsigned char ttl=255;
setsockopt(s,IPPROTO_IP,IP_MULTICAST_TTL,&ttl,sizeof(ttl));

struct in_addr addr;
setsockopt(s,IPPROTO_IP,IP_MULTICAST_IF,&addr,sizeof(addr));

unsigned char loop;
setsockopt(s,IPPROTO_IP,IP_MULTICAST_LOOP,&loop,sizeof(loop)); //参数loop设置为0禁止回送，设置为1允许回送。

struct ip_mreq 
{ 
    struct in_addr imn_multiaddr; /*加入或者退出的广播组IP地址*/ 
    struct in_addr imr_interface; /*加入或者退出的网络接口IP地址*/
};

struct ip_mreq mreq;
setsockopt(s,IPPROTO_IP,IP_ADD_MEMBERSHIP,&mreq,sizeof(mreq));

/*
*broadcast_server.c - 多播服务程序
*/
#define MCAST_PORT 8888;
#define MCAST_ADDR "224.0.0.100"/    /*一个局部连接多播地址，路由器不进行转发*/
#define MCAST_DATA "BROADCAST TEST DATA"            /*多播发送的数据*/
#define MCAST_INTERVAL 5                            /*发送间隔时间*/

int main(int argc, char*argv)
{
    int s;
    struct sockaddr_in mcast_addr;     

    s = socket(AF_INET, SOCK_DGRAM, 0);         /*建立套接字*/
    if (s == -1)
    {
        perror("socket()");
        return -1;
    }

    memset(&mcast_addr, 0, sizeof(mcast_addr));/*初始化IP多播地址为0*/

    mcast_addr.sin_family = AF_INET;                /*设置协议族类行为AF*/
    mcast_addr.sin_addr.s_addr = inet_addr(MCAST_ADDR);/*设置多播IP地址*/
    mcast_addr.sin_port = htons(MCAST_PORT);        /*设置多播端口*/
                                                    /*向多播地址发送数据*/
    while(1) {

        int n = sendto(s,                           /*套接字描述符*/
                       MCAST_DATA,     /*数据*/
                       sizeof(MCAST_DATA),    /*长度*/
                       0,
                       (struct sockaddr*)&mcast_addr,
                        sizeof(mcast_addr)) ;
        if( n < 0)
        {
            perror("sendto()");
            return -2;

        }  
    
        sleep(MCAST_INTERVAL);                          /*等待一段时间*/
    }

    return 0；
}

/*
*broadcast_client.c - 多播的客户端
*/

#define MCAST_PORT 8888;
#define MCAST_ADDR "224.0.0.100"     /*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;   
     
　　 /*加入多播组*/
    mreq.imr_multiaddr.s_addr = inet_addr(MCAST_ADDR); /*多播地址*/
    mreq.imr_interface.s_addr = htonl(INADDR_ANY); /*网络接口为默认*/

    /*将本机加入多播组*/
    err = setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq));//ASM模型
    if (err < 0)
    {
        perror("setsockopt():IP_ADD_MEMBERSHIP");
        return -4;
    }

    int times = 0;
    int addr_len = 0;
    char buff[BUFF_SIZE];
    int n = 0;

    /*循环接收多播组的消息，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);
    }

    /*退出多播组*/
    err = setsockopt(s, IPPROTO_IP, IP_DROP_MEMBERSHIP,&mreq, sizeof(mreq));
      
    close(s);
    return 0;
}