Socket s = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
s.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.MulticastInterface, ???);
s.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.MulticastInterface, ???);
s.SetSocketOption(SocketOptionLevel.IP, SocketOptionName.MulticastInterface, optionValue );