<snip> Investigate PPP. You can start a PPP server on one and a PPP client on the other and they will immediately be able to to talk and share data.
If all you need is remote login from one to the other investigate putting a console on the serial port of one machine then using something like Kermit or Minicom to log in. The advantage is it's really simple just to get a login that way rather than messing about with PPP, and Kermit/Minicom support file transfers if you need to dump files from one machine to the other. A
