mosquitto_pub and mosquitto_sub commands in IOT Protocols - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the mosquitto_pub command?

The mosquitto_pub command is used to send (publish) messages to a topic on an MQTT broker.

beginner

What does the mosquitto_sub command do?

The mosquitto_sub command subscribes to a topic on an MQTT broker to receive messages published to that topic.

beginner

How do you specify the topic when using mosquitto_pub?

Use the -t option followed by the topic name. For example: mosquitto_pub -t 'home/temperature'.

beginner

How can you receive messages from a topic using mosquitto_sub?

Use the -t option with the topic name. For example: mosquitto_sub -t 'home/temperature' will listen for messages on that topic.

beginner

What option do you use with mosquitto_pub to specify the message content?

Use the -m option followed by the message text. For example: mosquitto_pub -t 'home/temperature' -m '22.5' sends the message '22.5'.

Which command is used to subscribe to MQTT messages?

A mosquitto_sub

B mosquitto_pub

C mqtt_subscribe

D mqtt_publish

The mosquitto_sub command subscribes to topics to receive messages.

How do you specify the topic in mosquitto_pub?

A -m

B -t

C -p

D -q

The -t option sets the topic name.

What option sends the message content in mosquitto_pub?

A -m

B -t

C -s

D -c

The -m option specifies the message to publish.

Which command would you use to listen for messages on topic 'sensor/data'?

A mosquitto_pub -t sensor/data

B mosquitto_sub -t sensor/data

C mosquitto_pub -m sensor/data

D mosquitto_sub -m sensor/data

Use mosquitto_sub -t sensor/data to subscribe and listen to that topic.

What happens if you run mosquitto_pub -t 'home/light' -m 'ON'?

A It subscribes to the 'home/light' topic.

B It publishes the message 'ON' to the 'home/light' topic.

C It starts the MQTT broker.

D It deletes the 'home/light' topic.

This command sends the message 'ON' to the 'home/light' topic.

Explain how to publish a message to an MQTT topic using mosquitto_pub.

Think about how you tell the command where and what to send.

Describe how mosquitto_sub works to receive messages.

Focus on how you listen to messages from a topic.