TCP RTU Bridge: race condition with multiple clients

[zivillian]

Describe the bug
I'm connecting with two polling clients (evcc every 10s & nodered every 30s) to a TCP/RTU Bridge (heidelberg-1p3p). Every now and then I get the following error message in evcc:

heartbeat: modbus: response data size '28' does not match request quantity '1'

The response data size (28) matches the size of the requests I'm issuing from nodered, so it looks like one client receives a response from a different client.

If I'm correct the library is using millis() to assign a unique identifier to the bridge requests. After a quick search, it looks like millis() only has a resolution of 10ms, but even with 1ms resolution it may hit a collission.

Expected behavior
Clients only receive their own response.

To Reproduce
I was able to easily reproduce this with a small c# program running two clients with different request sizes in a loop (~15% collisions).

[Miq1]

Brilliant find! 💯

I will implement a better scheme to tell the responses from another.

[Miq1]

@zivillian Can you test again with the prerel branch? I changed the token to be micros() now that should change quickly enough to prevent duplicates.

[zivillian]

looks good - I've updated my project and my repo is no longer able to trigger the race

[Miq1]

👍🏻