Send messages from AC500 to mobile router. UDP?

I have an AC500 PM573-ETH that I wish to connect to a mobile router via ethernet, send a short message and have the mobile router send alarms via SMS (4G). I will also use the mobile router to gain access to the plc remotely. The router is NOT connected to the internet, just through the router on demand.

The mobile router supports alot of options, i.e. sockets and UDP messages and XML. Is UDP the way to go here? How do I set it up?

Or are there easier ways to do this?