April 2017
Intermediate to advanced
280 pages
6h 18m
English
Content preview from MQTT Essentials - A Lightweight IoT ProtocolBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Understanding callbacks
When we declare a function, we pass this function as an argument to another function or method, or we assign this function to an attribute, and then some code calls this function at some time; this mechanism is known as callback. The name callback is used because the code calls back a function at some time.
The code declares three functions that we will specify as callbacks:
on_connect: This function will be called when the MQTT client receives aCONNACKresponse from the MQTT server, that is, when a connection has been successfully established with the MQTT server.on_subscribe: This function will be called when the MQTT client receives aSUBACKresponse from the MQTT server, that is, when a subscription has been successfully ...
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