Check if this machine has a public IP address.
It checks all the network interfaces for IPv4 public addresses and returns true if one address is found.
    function OnGUI() {
        if (GUILayout.Button ("Start Server")) {
            // Use NAT punchthrough if no public IP present
            var useNat = !Network.HavePublicAddress();
            Network.InitializeServer(32, 25002, useNat);
            MasterServer.RegisterHost("MyUniqueGameType",
                "JohnDoes game", "l33t game for all");
        }
    }
        no example available in C#