Anyone know of a simple socket proxy in python?

[Sean True]

I've searched a bit and not found what I was looking for. I'm looking
for a bit of source code in Python that would run on a firewall and
connect external requests to internal TCP servers. Something like:

python plug.py hostname 80 21 23

would route all incoming connections to ports 80, 21, and 23 to an
internal host named 'hostname'.

I'll reinvent the wheel if necessary, but wanted to check. Comments on
the practicality of such a plug in Python are also welcome.

-- Sean