How do I test that two connected serial ports really transmit data?

Question

I have a device with two serial ports which I connected together, and I SSH into it. I would like to send data via one of the serial ports and read it from the other, to see that they do transmit/receive data.

I read on the topic but I'm confused about the various choice of programs that work with tty, and I don't know how to manage this process given that when I invoke one of these programs I either resign control to it, thus losing the ability to do other things besides using the port, or I get no control over it if I attempt to run it in the background.

How do I achieve my goal?

Answer 1

You could open an additional session with ssh and issue the following command in it:

tail -f /dev/ttyS0

it will print out everything that arrives at ttyS0. Of course, this solution is useful if you transmit printable characters only as otherwise your screen may be flooded with garbage.