If you really wanted to suffer it might be entertaining to use a Linux machine with some arbitrary number of USB serial dongles hanging off it as the "server" for a pile of SLIP/PPP host connections and then run whatever kind of packet driver-compatible network protocol over the top of that. USB serial dongles and a hub are cheap, most OSes have some kind of SLIP/PPP driver available, you can have it all this way. FTP, telnet, even NFS, the world is your oyster. Your slow, slow, so painfully slow-ouch-it-hurts-don't-touch-it oyster.