Odd - we're explicitly opening the device at that bitrate. If it only supports 4800 that might be a problem. Can you try to open it in a DOS box? You can just try something like
and that will show you the data if the bitrate etc are set correctly. Which can be done with a command called "mode". If it's just a matter of also supporting 4800 that should be easy enough to add on our end, but I need to know first if it works with mode and type.
Example MODE call (this one works for the device that we're using):
mode COM3 baud=9600 parity=N data=8
So first set mode for the COM port that you're using, then use type to see the input. If it looks like readable text (basically a lot of numbers separated by commas), it works.