Hi! I have created a simple chatting program a few years ago in python. The project consists of a server and a client. You run the server on any machine on a local network, and you run the client on any Windows computer connected to that network. The client has a nice and simple Graphical User Interface. If you're interested, I can let you see some screenshots and code samples if needed and if you like them I can sell you my code.
Contact me if you're interested.
Regards.