转：组播setsockopt:no such device问题的解决方法

当执行这个函数时：
setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP,&mreq, sizeof(mreq));
perror("error:");
打印错误：setsockopt:no such device

度娘原因：
What does "IP_ADD_MEMBERSHIP: No such device" mean? 

It means that the tool is trying to use multicast but the network interface doesn't support it There are two likely causes: 
·Your machine doesn't have multicast support enabled. For example, on Linux and FreeBSD it is possible to compile a kernel which doesn't support multicast.  
·You don't have a route for multicast traffic. Some systems don't add this by default, and you need to run：
route add -net 224.0.0.0 netmask 224.0.0.0 eth0(or similar). If you wish to use RAT in unicast mode only, it is possible to add the multicast route on the loopback interface.

我的板子是ZC706，刚开始，还以为是kernel不支持组播，运行了route add -net 224.0.0.0 netmask 224.0.0.0 eth0命令后，OK！！！