I have develop a library on C++ to control and monitor the PLC(Festo's CPX). I works very good (when it has proper connection).

Nevertheless I am experiencing a issue: sometimes the PLC does receive the messages (PC<-PLC), it is totally random, but once it starts working, it never fails while it is energized.
The work around is a power cycle, but it is annoying.

I have logged the UDP messages and I ca see that the messages are being broadcasted by the PC, but the PLC doesnt receive them. The PC->PLC communication always works

I got the idea from this project:
http://plclogger.sourceforge.net/index.php/en/

Has anyone experienced any issue like this?
Am i missing something?
How can I identify if this is HW issue or not? I happens with all the CPXs. Could it be a codesys RTE issue?

Thanks for your help

/Efrain