pubsubclient/_posts/2000-06-01-setCallback.md

tag, type, name, params, returns

tag	type	name	params	returns
api	function	setCallback	name description type callback a pointer to a message callback function called when a message arrives for a subscription created by this client. function*	type values PubSubClient* value description PubSubClient* the client instance, allowing the function to be chained

Sets the message callback function.