MQTT

A plain GET subscribes to the topic and prints all published messages.Doing a POST publishes the post data to the topic and exits.

Subscribe to the temperature in thehome/bedroom subject published byexample.com:

curl mqtt://example.com/home/bedroom/temp

Send the value75 to thehome/bedroom/dimmer subject hosted by theexample.com server:

curl -d 75 mqtt://example.com/home/bedroom/dimmer

What does curl deliver as a response to a subscribe

It outputs two bytes topic length (MSB | LSB), the topic followed by thepayload.

Caveats

Remaining limitations in curl's MQTT support as of September 2022:

• Only QoS level 0 is implemented for publish
• No way to set retain flag for publish
• No TLS (mqtts) support