Socat and RTU?!

[giulioiacom]

I'm trying to emulate two RTU ends using socat on my Linux machine. This is the socat call I'm running:
socat pty,raw,echo=0,link=/tmp/rtu0 pty,raw,echo=0,link=/tmp/rtu1

also, for reference, my RTU config is 19200 baud, N-8-1. On reconnect the master side context is fully torn down and rebuilt, so modbus_new_rtu() is called every time i stop/start the slave.

Aaand I'm noticing an erratic behavior, bear in mind that I'm fairly new to embedded programming (but not to systems).

My setup is fairly simple: a Modbus master polls a slave continuously, and I'm testing what happens when the slave process is restarted mid-run.. basically the result is that the master sometimes fails to reconnect and pick up where it left off.

I've done some reading and I understand that a socat PTY is not a perfect emulation of a real RTU serial layer, from my understanding there is some timing sensitive stuff that is not being emulated by the virtual ports (inter-frame silence, baudrate..etc)

What I'm basically trying to gauge is whether this kind of erratic behavior after a slave restart is expected or not - to be honest it's just personal sanity/curiosity at this point as I'm about to move the testing to a real hardware-based slave anyway, but I like knowing.. well everything.

Thanks in advance!!