OptionalexceptionFor an exception, the code the device answered with.
OptionalfoundWhat the reply named instead: the unit that answered, or the function it answered.
OptionalfunctionFor an exception or a reply to another function, the function asked.
Request, BroadcastRead, Port, Timeout, Frame, WrongUnit, WrongFunction,
Mismatch, or Exception.
The reason, in words.
OptionalreceivedFor a timeout, how many bytes of a reply had arrived.
The unit the transaction asked.
Why a transaction failed, for the facade to throw as a
ModbusClientError.