Establishing a p2p connection in python

[gs]

Hi!

This is my first time posting to a newsgroup so please be gentle to me
:)

Introduction to my problem:

I'm studying at the university and a lot of friends and I use MSN to
communicate. The problem is that MSN file sending/receiving
capabilities are terribly slow and has no resume option. We're also on
different subnets and can not access eachoters computers through smb
shares, nor can we have local ftp-servers.

My programming background:

I've been taking a few classes in JAVA, enough to get familiar with
sockets, threads and the most common sorting algortithms and
datastructures (binary trees, stacks etc). I'm also very comfortable
programming PHP on a webdeveloper basis.
I recently started out with Python and i immediatly fell in love with
it, and now I want to "master" it! :) Alas, my problem is also of
educational nature.

Setup:
We're about 30 friends who want the ability to share files.
We're spread out on about 3 different translated external IPs.
I have access to a public IP that has the ability to run python (but
not enough bandwith nor space to host an FTP).
I have limited programming experience.

Proposed solution:
I thought that one approach could be to write a small server for my
public server with the sole purpose of keeping track of connected
users and establishing p2p connections on demand.

Problems:
1) I've written a threaded server that stores information about
connected servers in a "container class". This class holds information
about username, a unique ID, the connecting adress and the actual
socket. I have not been able to find any information online on how i
could go about to connect two sockets. It would seem like the socket
is already "occupied" since it is connected to the server. Could one
duplicate, or otherwise get a dedicated socket for sending binary
data, to one connected socket from another? A few pointers and/or tips
would be greatly appreciated!

2) I've also failed to find python specific information on how abouts
one would do file resuming. I would think that you, somehow, use
md5-checksums to check file status and somehow skip the first part of
the datastream. Also, pointers and maybe an explanation in (short)
pseudo-code would be much appreciated.

3) Is this too big of a project for a novice programmer such as
myself? I do want to go through with this since it's a genuine
problem, but i do not know if i'm ready. I'm not a "quitter" per say,
but i'm afraid doing something TOO advanced in the beginning might be
overwhelming :)

Thanks for reading,
gs