Hi all,

I want to redirect traffic from one UART to another and I want to see how it is working.

For example,

1)
On an embedded board running busybox, I want to connect to /dev/ttyS0 (the only connector with pins on that board) and redirect to traffic to /dev/ttyS2 (where I can speak to another chip on that board).

I found solutions like this:
/bin/sh < /dev/ttyS0 > /dev/ttyS2 2> /dev/ttyS2 &

but at the moment it doesn't work.

How can test this on that embededded board or on a standard Linux PC?

I had the impression that I once did some simple test like having two xterm windows and doing in one "cat < / dev/ttyS1" and in the other "echo '123' > /dev/ttyS1" and I saw the string "123" appear in the window with the "cat" command.

Somehow that doesn't work not on the board (using two different telnet seesions) nor on the Linux PC.

(I looked after the permissions on thesse device nodes. I changed them with "chmod o+rw /dev/ttyS1" and I used sudo.)

I thought that somehow I got a poor understanding how an xterm window attaches to a tty device. Probably, the redirection works, only the xterm windows don't show it.

Can someone give me some specific reading to what I am probably missing or is there another way to test UART redirection without watching strings in xterm windows?

2)
Second problem is the program "ser2net" where I connect with a telnet session to different tty device nodes. The same thing here. How to test it?

I want to test it simply to know it's working and apply the working redirection solution, script, or program [I did one with open("dev/ttyS0"), read, and write] to the unresponding chip.

It is a bit hard to understand exactly what you're trying to accomplish. If I understand correctly, you have some onboard device which 'looks like' serial port /dev/ttyS2. You want to be able to connect to the device from some other actual serial device/terminal by physically connecting to the host's /dev/ttyS0 serial port (an actual serial port), and are looking for some method that transparently relays data between the respective serial ports. If this is not correct, please try to re-phrase your question, and perhaps provide more information about why you want to do this, and the underlying objective.
If this is correct, my best suggestion is either a fairly simple bit of C code to open each port, and perform the data relay through them that way. The existing program, socat, may be able to do this for you, but I'm not sure it works with serial ports.
--- rod.
EDIT: socat does evidently work with serial ports.

Thanks for your reply.

I found actually a method to reset this chip by shortening two pins and inside this chip is a test software with a welcome message that I can read with "cat < /dev/ttyS2".

I am still struggling with my C program and setting parameters with stty but I will give socat a go. Version 2.0.0 didn't compile for my MIPS processor (minor issues with "#if" and "&&" and an unknown definition) but version 1.7.2.0 did compile without problems.