Question

I have a program, using pyserial, and I want to test it without using a real serial port device.

In windows, I use com0com, and in linux, I know there is a method to create virtual serial port pair without using additional program.

so I look up the manual, and found pts, /dev/ptmx, but I don’t know how to create a pair by following the manual, can anyone give me a example?

I tried(in python):

f = open("/dev/ptmx", "r")

and it works, /dev/pts/4 is created.

and I tried:

f = open("/dev/4", "w")

and the result is:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IOError: [Errno 5] Input/output error: '/dev/pts/4'

edit:
I found a solution(workround), using socat.

socat PTY,link=COM8 PTY,link=COM9

then COM8 COM9 are created as virtual serial port pair.

Answer 1

Per the docs, you need ptsname to get the name of the slave-side of the pseudo-terminal, and also, quoting the docs,

Before opening the pseudo-terminal
slave, you must pass the master’s file
descriptor to grantpt(3) and
unlockpt(3).

You should be able to use ctypes to call all of the needed functions.