[outworlder]

Get off my lawn!

Telnet requires a functioning network stack.

Before we had that, we had modems, which I assume was the case since wardialing is mentioned. They could run ANY protocol - or indeed none at all. You could tie it directly to the text I/O of any program(easy on unix systems, not as easy on MSDOS or early Windows versions). Many "BBS" systems worked this way.

EDIT: also early "multiplayer" games, which would talk to the modem directly. I've spend hours playing Descent over a 9600bps modem connection. That was only running... whatever protocol Descent used. You kids and your fancy packets.

If a file was being transferred you could do nothing else. If you were specially high-tech, you would use ZModem for the transfer. If not, you would be using something like XModem, or even Kermit or something proprietary.