core: Modbus register 0 [Errno 104] Connection reset by peer - reopen

The problem

Reopen of issue #49749. I had reported this back in April; fixes had gone in, but in the mean-time I’d been running the old modbus integration from 2021.1.4 as a custom component. Today I had a chance to load up the current dev branch and do some testing. The issue still exists.

Once encountered the socket becomes closed and is never retried.

I have a development environment loaded up and will work on debugging this issue and create a PR. Please assign to me.

What is version of Home Assistant Core has the issue?

2021.7.1

What was the last working version of Home Assistant Core?

2021.1.4

What type of installation are you running?

Home Assistant Container

Integration causing the issue

modbus

Link to integration documentation on our website

https://www.home-assistant.io/integrations/modbus/

Example YAML snippet

modbus:
  name: hub1
  type: tcp
  host: 192.168.1.5
  port: 502
  sensors:
    - name: OldWell
      scan_interval: 10
      unit_of_measurement: Amp
      address: 0
      data_type: uint
      scale: 0.00061036
      offset: -20
      precision: 3
      input_type: input
    - name: NewWell
      unit_of_measurement: Amp
      address: 1
      data_type: uint
      scale: 0.00061036
      offset: -20
      precision: 3
      input_type: input

Anything in the logs that might be useful for us?

2021-07-08 06:36:21 DEBUG (SyncWorker_0) [pymodbus.client.sync] New Transaction state 'SENDING'
2021-07-08 06:36:21 ERROR (SyncWorker_0) [homeassistant.components.modbus.modbus] Pymodbus: Modbus Error: [Input/Output] [Errno 104] Connection reset by peer

Additional information

No response