[转]IP_ADD_MEMBERSHIP : 组播错误 的解决方法：

http://www.cnitblog.com/dvb-dvb/archive/2012/10/15/aa.html

by default live library includes winsock.h through windows.h instead of winsock2.h, but requires Winsock 2 in  initializeWinsockIfNecessary(...) function.
IP_ADD_MEMBERSHIP value for Winsock1 is 5, and for Winsock 2 is 12.
Therefore
socketJoinGroup(...) function is trying to call
setsockopt(IP_ADD_MEMBERSHIP) from Winsock 2 with optname from Winsock
1.
There is the confusion between Winsock versions.

live555的 组播的code如下 :

testAddr.s_addr = our_inet_addr("228.67.43.91"); // arbitrary
      Port testPort(15947); // ditto

sock = setupDatagramSocket(env, testPort);
      if (sock < 0) break;

if (!socketJoinGroup(env, sock, testAddr.s_addr))
   {
    env<<"Failed to socket Join Group\n";
    break;
   }

结果：

if (setsockopt(socket, IPPROTO_IP, IP_ADD_MEMBERSHIP,
   (const char*)&imr, sizeof (struct ip_mreq)) < 0) {

一直失败：错误提示为： 10042：

修改为： if (setsockopt(socket, IPPROTO_IP, 12,
   (const char*)&imr, sizeof (struct ip_mreq)) < 0) {

因为不同的socket版本，定义IP_ADD_MEMBERSHIP 的值不同：

in socket ver1.0中：
＃define IP_ADD_MEMBERSHIP 5

in socket ver2.0中：
＃define IP_ADD_MEMBERSHIP 12