I can implement a console program that does this for you. How soon do you need the work done?
This bid is for monitoring the *incoming* serial port traffic only - not the outgoing also. (If you need to 'sniff' the outgoing traffic also that is a different kettle of fish - and I would need to revise my bid.)
I would use the C language, and test on a Debian Linux system. I have USB-serial converter to test - and can send dummy test data over the serial port from an Arduino or Raspberry Pi.
To be clear: I am offering to develop a *console* program - not a program with a GUI (graphical user interface). I might be able to provide a GUI also (e.g. using GTK), but I would have to treat that as a *separate / additional milestone*.
NOTE: Until I have full details, this bid is PROVISIONAL. I may need to adjust the price and / or timeframe.
I am based in Ireland - GMT timezone.