Screen vs. socat

Question

There is already a question: Screen fails to release pty and there is no answer (only a workaround has been provided so far).

My case is different and I would like to know the answer to the original question. So, why does socat (even recent version 1.7.3.0) ignore the screen when the last closes the pipe?

Answer 1

The answer is very simple at the end. We have to use open('/dev/ptmx') instead of old openpty() mechanism.