Bridge Serial-Ports over network

Question

For an application, which uses SerialPorts for communication (Modbus RTU, to be exactly) I need to bridge the SerialPort over the network for testing purposes.

So I would like to have the following Setup:

Device        |     Network      |      PC

SerialPort    |------------------|    SerialPort
Map Serialport|                  | Map network to Serialport
   to Network |                  |   

I already got the first part working with socat.

I opened the TCP Port on PC with

nc -l 8080

On my Device I used

socat  pty,link=/dev/virtualcom0 tcp:PC-IP:8080

To map everything written on /dev/virtualcom0 to PC-IP on port 8080.

But now I have problems to map the socket back to a Serialport.

socat tcp:PC-IP:9123 pty,link=/dev/virtualport0

This got me a Connection Refused, which is obvious because i used TCP and the Port is already used by the Device.
So I tried the same with

socat  pty,link=/dev/virtualcom0,raw  udp:PC-IP:8080

and changed everything else to UDP, too.

But then nothing arrives on my /dev/virtlalcom0/ on my PC.

Answer 1

One side of the tcp connection needs to be listening on the port (the first one you launch), and the second side connects to it.

For the first side do:

socat tcp-listen:8080 pty,link=/dev/virtualport0

And for the second side do:

socat pty,link=/dev/virtualcom0 tcp:IP-of-other-machine:8080

Forget the netcat, you do not need it.