I had this question and the folk had no clue that the vinyl cutter had to be on COM1. They had someone set it up years ago and then moved to a new machine and thought all they needed was DOS (or dosbox.)
Since the new machine had the COM port at 2 they flailed away at this for months without telling anyone the details so no one guessed it was the COM port setting in the DOS app.
Luckily I heard about it and had a little knowledge that the com port mattered and they were able to make it work the next day.
After down load dosbox how do I use it to run a specific program that operates an engraving machne based on dos?