Nov.05.2017 -- 4:20pm
I was able to get IBM PC DOS 7 installed, and Watcom for DOS installed. Everything worked and compiled. I discovered the code I had from the code examples were expecting Turbo C++ 2.0 for DOS, so I was able to locate that online and install it. It also worked and compiled. It also has nice integrated DOS-based tools including a nice debugger, so I'll probably use that in moving forward.
At least one of the machines I'm using does not support EPP+ECP hardware, so I'll fall back on regular parallel protocols. It will be slower, but still at least 20x faster than serial. For right now, I'm going to try to get serial communications working at 115.2 Kbps in OS/2, and then in ES/2.