Close an open connection to an MQTT broker
Optional function called upon disconnection
This document describes pre-release alpha functionality which is not yet available to developers.
Both the documentation and the functionality it details are preliminary and subject to change.
This method closes the mqttclient’s connection to its specified MQTT broker.
Optionally, you may provide a function which will be called when the connection has been closed. The callback function should have no parameters of its own.