If you have a dedicated server set up for Open Arena, you can control it either using the command console and rcon on the client side – or by typing in the commands directly into the server process (oa_ded).
But how is it possible to access the server from within a different script or application, or if the server process is not bound to a shell?
First of all, install netcat if you don't happen to have it already on your system.
The trick now is to prefix every command by four non-breaking spaces (255). Thus it's recommendable to write a small shell script for that:
#!/bin/bash echo $'\377'$'\377'$'\377'$'\377'"rcon $2 $3" | nc -uw0 $1 27960
You can now easily control the server directly from the command line:
chmod +x rcon.sh ./rcon.sh 127.0.0.1 myRconPassword "say Hello"
Of course it's not only possible to send some texts but – for example – to also change the current map or to set some variables. This allows for easy scripting of the server.