thank you very much for your quick reply. It was exactly what I needed, and I was able to solve my issue. I'm implementing this protocol analyzer for the first time while figuring out how it works. Definitely some refactoring is necessary afterwards. Thanks for your help.

I'd say it's a better practice to keep state variables as member fields of your parser class rather using globals. But it's not written in stone, of course.

To reset state vairables/fields on every session start, process log.StdRecordCode.SessionStart in your log.Converter.convert(...) routine and do initialization from there. Also, you want to override log.Converter.reset() and do initialization here, too (reset() will get called when a user force-clears the log, rebuilds the log by adding a filter, etc).

You can check the official Modbus Analyzer for reference (there are two versions now, a new one based on dynamic layouts and the legacy once).

Also, there're new tutorials on writing protocol analyzers and packet templates using dynamic layouts, check it out:

https://ioninja.com/doc/developer-manual/tutorial-plugin-analyzer.html
https://ioninja.com/doc/developer-manual/tutorial-ias-packet-dylayout.html