I'm going to make a wild stab in the dark here:
You are just runnning the application up in Visual Studio (or the client and server are on the same machine), the IP you are getting is 127.0.0.1? If som, this is correct, you need to test across two machines.
One further option is that the client machine is coming from behind a coporate firewall/ NAT proxy / VPN. If that is the case then it you will probably get a single IP for the whole network. See:
http://forums.asp.net/t/1053767.aspx[
^] for a fuller explanation and more details.