HOW-TO: Virtual Serial ports in Linux

The below instructions are targeted toward CentOS but should work on other Linux Distributions.

This HOW-TO shows how to create 2 virtual serial ports that are linked together as if they were 2 physical serial ports linked together using a NULL-modem cable.

1. Install socat

yum install socat

2. Run socat in a screen instance

screen socat -d -d pty,raw,echo=0 pty,raw,echo=0

You will see something like this on your screen

2012/11/15 15:52:43 socat[24000] N PTY is /dev/pts/2

2012/11/15 15:52:43 socat[24000] N PTY is /dev/pts/3

2012/11/15 15:52:43 socat[24000] N starting data transfer loop with FDs [3,3] and [5,5]

Your first serial port is /dev/pts2 and your 2nd serial port is /dev/pts/3 (those port path can be different from this example). Those will remain linked as long as the socat program is running.

Press CTRL-A d in order to detach from this scree instance

3. Configure and run your first application using /dev/pts/2

4. Configure and run your second application using /dev/pts/3

Voila your 2 applications are communicating using the 2 virtual serial ports.

Note that this is just one application of the socat program. You can for instance link a serial port with a TCP socket and much more. 

Here are some nice links regarding socat

https://help.ubuntu.com/community/VirtualSerialPort

http://justcheckingonall.wordpress.com/2009/06/09/howto-vsp-socat/

http://www.dest-unreach.org/socat/doc/socat.html