Question

您好
我试图在具有两个NIC的机器上编写多播客户端，但我无法使其工作我可以看到一个嗅探器，一旦我启动程序，NIC（eth4）开始接收多播数据报，但是，我的程序中无法接收（）任何内容。当运行“tshark -i eth4 -R udp.port == xxx（多播端口）”
时我明白了：
1059.435483 y.y.y.y. （一些ip） - ＆gt; z.z.z.z（multicast ip，not my eth4 NIC IP）UDP源端口：kkk（其他一些端口）目的端口：xxx（组播端口）

在网上搜索了一些示例/解释，但似乎我做了其他人所做的事任何帮助将不胜感激...
谢谢！

bool connectionManager::sendMulticastJoinRequest()
{
    struct sockaddr_in localSock;
    struct ip_mreqn group;

    char* mc_addr_str = SystemManager::Instance()->getTCP_IP_CHT();
    char* local_addr_str = SystemManager::Instance()->getlocal_IP_TOLA();
    int port = SystemManager::Instance()->getTCP_Port_CHT();
    /* Create a datagram socket on which to receive. */

    CHT_UDP_Feed_sock = socket(AF_INET, SOCK_DGRAM, 0);

    if(CHT_UDP_Feed_sock < 0)
    {
        perror("Opening datagram socket error");
        return false;
    }
    /* application to receive copies of the multicast datagrams. */
    {
      int reuse = 1;
      if(setsockopt(CHT_UDP_Feed_sock, SOL_SOCKET, SO_REUSEADDR, (char *)&reuse, sizeof(reuse)) < 0)
      {
          perror("Setting SO_REUSEADDR error");
          close(CHT_UDP_Feed_sock);
          return false;
      }
    }

    /* Bind to the proper port number with the IP address */
    /* specified as INADDR_ANY. */
    memset((char *) &localSock, 0, sizeof(localSock));
    localSock.sin_family = AF_INET;
    localSock.sin_port = htons(port);
    localSock.sin_addr.s_addr =inet_addr(local_addr_str); // htonl(INADDR_ANY); //
    if(bind(CHT_UDP_Feed_sock, (struct sockaddr*)&localSock, sizeof(localSock)))
    {
        perror("Binding datagram socket error");
        close(CHT_UDP_Feed_sock);
        return false;
    }

    /* Join the multicast group mc_addr_str on the local local_addr_str */
    /* interface. Note that this IP_ADD_MEMBERSHIP option must be */
    /* called for each local interface over which the multicast */
    /* datagrams are to be received. */

    group.imr_ifindex = if_nametoindex("eth4");
    if (setsockopt(CHT_UDP_Feed_sock, SOL_SOCKET, SO_BINDTODEVICE, "eth4", 5) < 0)
        return false;
    group.imr_multiaddr.s_addr = inet_addr(mc_addr_str);
    group.imr_address.s_addr = htonl(INADDR_ANY); //also tried inet_addr(local_addr_str); instead
    if(setsockopt(CHT_UDP_Feed_sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&group, sizeof(group)) < 0)
    {
        perror("Adding multicast group error");
        close(CHT_UDP_Feed_sock);
        return false;
    }

    // Read from the socket.
    char databuf[1024];
    int datalen = sizeof(databuf);
    if(read(CHT_UDP_Feed_sock, databuf, datalen) < 0)
    {
        perror("Reading datagram message error");
        close(CHT_UDP_Feed_sock);
        return false;
    }
    else
    {
        printf("Reading datagram message...OK.\n");
        printf("The message from multicast server is: \"%s\"\n", databuf);
    }
    return true;
}

Answer 1

在致电 IP_ADD_MEMBERSHIP 之前设置群组：

group.imr_multiaddr.s_addr = inet_addr(mc_addr_str);
group.imr_address.s_addr = inet_addr(local_addr_str);

您可以在此之前将呼叫保留在 SO_BINDTODEVICE ，但只有在您只想使用一个特定界面时才有必要。

Answer 2

我完全按照这样设置了组（代码已更新）我还添加了路由表“route add -net 224.0.0.0 netmask 240.0.0.0 dev eth4”
仍然没有成功。
除了那之外我还需要在我的环境中设置什么？

在使用多个NIC的C ++中侦听多播时出现问题

2 个答案: