I try to keep variables to a minimum. Thus I carry a old compaq laptop PC running WIN95 (which is true DOS) and I have EZUTLS (from EZCAM) version 0 loaded on it. I have a box of cables (plus various adapters) I made 18 years ago for communication to a FANUC, Heidenhain, Bridgeport BOSS, and FMDC board. I also have a device that is a in line RS232 tester, 25 pin, with LED on the necessary lines that can light up either red or green. This was purchased at radio shack.
I first make sure that the communication parameters are correct. Baud rate, stop bits, data bits, parity, etc.
I then try and dump a program to and then from the machine. I can watch the LED lights to see if data is being sent. They flicker.
If data is being sent to the machine but not received, then you may have a machine problem. From the machine to the PC but not received, a PC problem. ETC.
But I keep certain items constant. My PC, cable, software, etc.
If communication works for me, then I have it narrowed down to the customer equipment. I then substitute items one at a time. I do not bother with software that was not standard issue (supported) by Bridgeport.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)