Chat Relay
What is it?
The CheckValve Chat Relay is a program developed in Java which receives log data from HLDS/SRCDS servers, filters out player chat messages, and relays those messages on to a client such as the CheckValve app.
What's required?
The Chat Relay does not need to run on the game server; it can run on any machine, as long as the machine is able to accept traffic from game servers and clients on the ports specified in the Chat Relay configuration.
The Chat Relay works with any SRCDS or HLDS server using the built-in chat functionality. It does not require any plugins or server changes, except for the addition of a logaddress_add command in the server's configuration.
See Using the Chat Relay for more information.
Documentation
Documentation for the Chat Relay can be found here:
Chat Relay protocol details (packet types and formats)
SourceMod Plugin
If you're using SourceMod, you may prefer the CheckValve Chat Relay plugin contributed by 341464. This plugin implements all of the core features of the Chat Relay and is a great alternative to the stand-alone Java application. Check it out!