c# 特定源组播该怎么写？

[dota3c]

我在网上查到的是这样写的，但是发现收不到数据，但是登陆交换机发现组播路由表已经建立起来了，接收的有，但是转发是0，
这段代码哪里有问题。
文章地址：http://blog.csdn.net/guoweifeng1987/article/details/11715903

Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 5980);
s.Bind(ipep);
byte[] membershipAddresses = new byte[12]; // 3 IPs * 4 bytes (IPv4)
Buffer.BlockCopy(multicastIp.GetAddressBytes(), 0, membershipAddresses, 0, 4); //组播地址
Buffer.BlockCopy(sourceIp.GetAddressBytes(), 0, membershipAddresses, 4, 4); //组播源地址
Buffer.BlockCopy(localIp.GetAddressBytes(), 0, membershipAddresses, 8, 4); //本地接收地址
socket.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.AddSourceMembership, membershipAddresses);