Programming :: Cross-platform LAN File Exchange Program?

I recently faced a problem. At my college, I linked my laptop with my friend's laptop with an ad-hoc wifi network. I wanted to send him a file. I was running Ubuntu, and he was running XP. Unfortunately, I could not find an easy way to send him the file. Another problem I faced was when I wanted to transfer the contents of my hard disk to another computer. I had to install Filezilla server on the other computer, and upload the files from one computer to the other.

I feel that its a really cumbersome method of transferring files in the same network. Mobile phones have bluetooth, and a file can be sent to another mobile very easily without any fuss. Does anyone know whether any such program exists already? If not, I want to write such a program that will allow one user to add another user to a personal network, and send or recieve files and/or communicate in other ways. The only language I know is Python (self-taught). I was wondering what GUI framework to use. I've never written a GUI program before, and would like to hear your opinions. This will be a very basic program, and must be able to run on many platforms.