Error: unpack_from requires a buffer of at least 4 bytes about pylogix HOT 4 CLOSED

Thanks for posting the code you are using, this will be very helpful. I'll dig into this as soon as I get a chance.

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First, when you are passing the instance of PLC() to your functions, it is named PLC, I would not do it that way because the module is named the same.

Second, put a small delay between starting your threads, say 100ms. Your second thread is requesting data before first thread has established the connection, so it's trying to establish the connection twice.

Let me know how this works for you.

main (2).txt

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This improves it a little bit, but I do still run into this error rarely (something like once every 100 starts). The more reliable solution I have found is to just not share the PLC object between the threads -- let each thread have its own instance.

Thanks a lot!

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That is actually the way I would do it. Have an instance per thread. That is my test I did initially, then I worked my way back to closer what you were doing.

Your code will be pretty useful to me I think. I will do some more stability tests and it should help come up with better error handling.

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