To receive messages on V16Pro
Setup a "Device" as manufacturer "Custom" and model "Custom". Select a specific UDP port rather than leaving the default of "0" (for example 5000). Have the other system send whatever strings you'd like to port 5000. For example, use the text "startmain\r". You could use any text you'd like. Setup a "message" type trigger for each sequence by clicking on the "triggers" button in the sequence view. You can setup any response you'd like back to the other system using the "Message Out" command.
To send messages to the AMX
Just use the V16Pro's "Message Out" command on the custom device you setup (see above).
Or, you could also create a really simple "product file" in place of the "custom" so you can have your pre-set messages to the AMX (whatever they may be) stored in a nice file. This is easy to do with "Product File Creator" under the "Tools" menu. .
See Article for on Starting Sequences for more information on ways to start sequences in the V16Pro/V4Pro.