第21章 多播

时间:2022-05-03
本文章向大家介绍第21章 多播,主要内容包括其使用实例、应用技巧、基本知识点总结和需要注意事项,具有一定的参考价值,需要的朋友可以参考一下。

1·多播(组播)地址:224.0.0.0~139.255.255.255

2·发送多播数据报无需任何特殊处理,发送应用程序不必为此加入多播组

3·多播相对于广播的优势在于不会对多播分组不感兴趣的主机增加额外负担

#include "../Gnet.h"

int main(int argc, const char* argv[])
{
    int sendfd, recvfd;
    const int on = 1;
    //const int off = 0;
    struct sockaddr_in sockaddr;
    socklen_t addrlen;
    struct ip_mreq mreq;
    int nrecv;
    char buf[MAX_LINE];
    char addrstr[INET_ADDRSTRLEN];

    if(argc != 2)
        perr_exit("usage: mcast <IP-multicast-address>");

    sendfd = Socket(AF_INET, SOCK_DGRAM, 0);
    recvfd = Socket(AF_INET, SOCK_DGRAM, 0);

    if(setsockopt(recvfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
        perr_exit("setsockopt error. 22");

    sockaddr.sin_family = AF_INET;
    //sockaddr.sin_port = htons(SERVER_PORT);
    if(inet_pton(AF_INET, argv[1], &sockaddr.sin_addr) < 0)
        perr_exit("inet_pton error.27");
    addrlen = sizeof(sockaddr);
    Bind(recvfd, (struct sockaddr*)&sockaddr, addrlen);//接收套接字绑定多播地址

    mreq.imr_multiaddr = sockaddr.sin_addr;
    //inet_pton(AF_INET, "192.168.17.129", &mreq.imr_interface.s_addr);
    mreq.imr_interface.s_addr = htonl(INADDR_ANY);

    if(setsockopt(recvfd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) <0)//接收套接字加入多播组
        perr_exit("setsockopt error.35");
    //setsockopt(sendfd, IPPROTO_IP, IP_MULTICAST_LOOP, &off, sizeof(off));
    if(fork() > 0)
    {
        while(1)
        {
            nrecv = recvfrom(recvfd, buf, MAX_LINE, 0, (struct sockaddr*)&sockaddr, &addrlen); 
            printf("from %s: %sn", 
                   inet_ntop(AF_INET, &sockaddr, addrstr, sizeof(addrstr)), buf);
        }
    }
    else
    {
        while(1)
        {
            sendto(sendfd, "test data", strlen("test data")+1, 0, (struct sockaddr*)&sockaddr, addrlen);
            sleep(2);
        }
    }

    return 0;
}

github:https://github.com/gongluck/unp-notes