Remote networking C#

Thanks: I'm working on this project, and am required to build a small windows application that will be used as a chat system on LAN, i want users to be able to chat from two different computers on the network, e.g there should be two textboxes one for writing the message and one for reading responses from other end, i tried it but it only works on one computer and i donot want to have client application separated from server application if that is possible: help me with C# code please: I'm new to C#: and am using windows XP pro as (OS) thankyou in advance for your support