Thanks for the detailed explanation and information Vladimir! This fixes my issue and nice to hear that it will be solved in the next release. Thank you very much!

I'm using the mobuds TCP packet template in the transmit pane to test reading some holding registers. So default I'm using the "Modbus TCP read" option and fill in all the necassary options. After trying to use the "Modbus TCP read/write multiple" and switched back to "Modbus TCP read" I cant read any register anymore without getting the IllegalFunction Exception. I have tried resetting all the settings back to default, even reinstalled IOninja but with no success.

I can reproduce this issue on another PC. When I'm comparing my settings on a fresh install of IOninja, the issue seems to be the length field of ADU what is updating wrong. When I disable "auto-update length" and fill in the value from the PC that is working correctly, it's working, but when I enable "auto-update length" again its throwing the illegalfunction exceptions again.

Is this is bug or am I missing something?

Succesvol reading with auto-update disabled

Failed to read with auto-update enabled