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As I recall from my college work-study program forty years ago, that's the way we wired up RS-232 terminals: four wires, two of them ground. My memory is no longer great, but I know we had 25-pin connectors, and I'm thinking in that world pin 1 was ground, 3 & 4 swapped, and 8? was a second ground. I have nothing to help you, but thank you for bringing back memories of some good times!
Must have been 1, 2, 3 & 7. A forty year span is a LONG time to maintain an image in one's mind. Connecting terminals to a PDP-11/34; life was simple back then. Old men want a time machine because the past looks better, or at least longer, than the future.
You're right. You only need 3 wires for duplex communication. Assuming you connected these wires correctly. the next question is what kind of cable are you using. Transmission lines cause reflections and energy loss. At 10 feet, your cable is long enough to be affected by it. If you're using 3 loose wires, that's a problem; try twisting the wires together. Ideally, you want 100 ohm impedance with 24 AWG wire. If you're using a pre-built cable, check the specs. It may be designed for something else. I also suggest you make sure both computers are powered from the same circuit; otherwise, you may have issues with ground loops.
I have a whole box of serial cables that I have accumulated over 20 years of use. I have male-female, female-female, and male-male straight-through cables, and a null modem cable. This lets me make up whatever is called for. I verify my connection using one or two of these cables, then build a custom cable. If the custom cable doesn't work, I know it's the cable.
You can connect a serial port using only transmit, receive, and ground, but even at 9600 baud, a steady stream of bytes is likely to overrun your PC's receiver buffer. That's why you want to connect RTS and CTS, which do hardware handshaking. You can do software handshaking using XON and XOFF if your USB-serial box understands that and your terminal software understands that.
No need. The mystery - why did one cable work and the hand made cable didn't - answered by checking the source code. If you ask for handshake, you need to provide the appropriate cabling. Simple brainfart on my part.
<italic>Stuck in a dysfunctional matrix from which I must escape...
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