Modbus server

[FloMeyer]

What does this implement/fix?

Types of changes

• [ x] Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#

Test Environment

• [ x] ESP32
• ESP32 IDF
• ESP8266
• RP2040

Example entry for config.yaml:

# Example config.yaml

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[JeroenVanOort]

Thank you very much for spotting this! It took me a while to get my head around, but I now understand what happens: after a match is found, the code keeps matching consecutive registers without checking if the requested number of registers has already been met. The simpler solution seems to break after a match. I will update my PR with this and test it on my local device.

[JeroenVanOort]

Thanks again for spotting this problem. I have fixed it in my PR, but using a simpler approach.