The binding docs tell you howto get DEBUG logging for further diagnostics.
But I don’t think there’s much more to see with “Connection refused”.
Modbus slaves are entitled to say “Nope, I’m busy, go away”. There are neater ways to say that, but many Modbus slave implementations are uhhh crude and dirty.
If that’s the problem, there’s little you can apart from tuning your retry strategy perhaps.
But just as likely is that the slave is sluggish handling rapid TCP
connect/reconnect requests.
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