Serial communications between R1 and S1

Before you say - “why are you using serial comms, not ethernet” you have to know this is a (poorly) built system created by another integrator who has long been out of business. The reason for the serial is the PACs are 1/4 mile away and this integrator used a serial communications modem to span the distance. I am trying to get the customer to let me replace the serial modems with ethernet modems and convert the code but he is very hesitant at this point.
Anyway, on to the feature story!.
Does anyone have sample code to pass a few bits back and forth between an S1 and and R1? I am running his code on my bench. The S1 transmits and the R1 receives. and the R1 transmits but the S1 is not receiving. I am just trying to find the most basic serial code which I can use as a test on my bench so I can then start to repair his (crappy) code.

I think it should be as simple as setting the comm handle value with the matching baud rate.
That should be all there is to it.

This post gives such an example.