How do I subscribe to all topics of a MQTT broker

Question

I want to connect a client which will monitor all the topics of the broker to respond to the events when I don t know what are names of topic

User · Answer

Use the wildcard     but beware that at some point you will have to somehow understand the data passing through the bus

User · Answer

Concrete example  mosquitto org is very active  at the time of this posting    This is a nice smoke test for a MQTT subscriber linux device      mosquitto sub -h test mosquitto org -t     -v   The     is a wildcard for topics and returns all messages  topics   the server had a lot of traffic  so it returned a  firehose  of messages   If your MQTT device publishes a topic of irisys V4D-19230005  to the test MQTT broker   then you could filter the messages    mosquitto sub -h test mosquitto org -t  irisys V4D-19230005    -v   Options    -h the hostname  default MQTT port   1883  -t precedes the topic

User · Answer

Subscribing to   gives you a subscription to everything except for topics that start with a    these are normally control topics anyway    It is better to know what you are subscribing to first though  of course  and note that some broker configurations may disallow subscribing to   explicitly

User · Answer

You can use mosquitto sub  which is part of the mosquitto-clients package  and subscribe to the wildcard topic     mosquitto sub -v -h broker ip -p 1883 -t

[mqtt] How do I subscribe to all topics of a MQTT broker

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