Can you send a TCP command from the AMX system directly over network?
refer to the Catalyst webserver for details how to do this or the notes in the Custom serial commands.

Otherwise if you can do it via a MIDI command, but by using an RS232 interface...
MIDI commands can be sent over RS232 - its just HEX data...
Configure the MIDI input trigger to work, but just select an RS232 interface rather than a MIDI interface
Then write the MIDI HEX data command to send from your AMX control system.

Have done both methods a while ago - but not tested recently.

S