The Ricochet Robot Game Server implements the Ricochet Robot Game Protocol to permit multiple users to share a Ricochet Robot game. The server can be found in the ricochet repository
While the protocol is usable through an ASCII telnet interface, it is much easier to play with a graphical client. Two such are available in git, the nickle/nichrome/cairo-5c version in the ricochet repository and a gtk version in the grrobot repository
Instructions for accessing these repositories can be found in the keithp.com git instructions.
Feel free to use the rr game server on port 5252 (the default for most of these applications) on rr.nickle.org.