I have been using a DOS program for a few years now to control heating and cooling automation systems in buildings from my office. I use a 56k modem through a serial port to connect because that is the simplest way to interact with the program. Recently, the computer finally met its demise, and I had to start using a newer computer (running XP).

I got the program on and am attempting to use DOSBox to run it. The program opens runs fine, and after setting COM 1 to a realport as a serial connection (I'm using the same modem), everything seemed to connect. I can receive data that tells me the current environment in the building, but when I try to make changes, there seems to be a communication error, and I'm just about out of ideas.

Any suggestions? Thanks.