Response "MQTT"
(1) The MQTT alias. See section MQTT connections.
(2) The topic to which the message is sent.
(3) Die Übertragungsqualität (Quality of Service, QoS).
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At most once |
The lowest-cost in terms of volume of data transfer. This is suitable if you have a reliable connection between Lobster_data and the MQTT broker. |
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At least once |
A good choice if you need to be sure every message gets through and the receiving application can tolerate receiving a message more than once. |
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Exactly once |
Guarantees delivery exactly once, but has a relatively high cost in terms of data transfer. |
System variables
In MQTT version 5, you can use system variables of the form MQTT_<keyname> to pass user properties (key, value). See also MQTT_SYS_CONTENTTYPE and MQTT_SYS_CORRELATIONDATA.