This section by Andreas Koch.

- Modem Chess, a PD game in Basic by ???
- Modem-Battleships, a PD game in Basic by ???
- Tele-Chess, a PD game in Basic by ???
- Jelly Beans a ML game by Chris Martin
- "Battleships ST-XL" by Florian Dingler
  (German name: Schiffe versenken ST-XL)
- Midi Maze by XANTH (prototype)
- Commbat by Adventure International

(I have also seen an advert from GCP in ANALOG or Antic, that listed
 the following games: The City, Cybertank, Cybership, Bio-War, Lords
 of Space; I am not sure if they are all available for the Atari, A.K.)

To play these games online, one would not only require an Atari computer,
but also a modem, a modem-driver and/or a terminal program (like Kermit,
Bobterm, Teleterm, A-Term, Ice-T, BBS Express Pro, etc.). See also the
sections 7.8, 10.1 and 10.2 which tell you more about modem/terminal
programs and modem hardware for the Atari. Emulator users have it a little
easier and can use the built-in modem emulation in Ape-DOS, Ape-Win,
Atari 800 DOS, Atari 800 Win, etc.