[gnu.announce] Network connection gateway?

tower@WHEATIES.AI.MIT.EDU (Leonard H. Tower Jr.) (10/07/88)

Forwarded-For: rms@wheaties.ai.mit.edu (Richard Stallman)

I am looking for a network server that would accept connections on a
specified port and handle them by opening another connection to that
same port on a prespecified machine and sending all data through in
both directions.  The idea is to allow one machine to hand off all
mail traffic to another machine, and not have to run a real mailer at
all.

This would probably not be very hard for a person familiar with
network software to write, but it might be painful to debug.  So I
wonder if such a program already exists.  Does anybody know of one?