Is there a RS232 Library that people would recommend?

[Shintaro]

Hi,
I have an old 6809 trainer that  uses Procom for terminal and file up load.

Can anyone recommend a RS232 library that I can use to interface with the trainer?
I would like to just create a simple terminal program and maybe the ability to up load a file.
It has been a wish of mine since I built the darn thing back in 1990.

It would be nice to take it further, but one step at a time.
The goal at the moment is just the Terminal.

Regards.