MQTT in curl

Usage

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

Example subscribe:

curl mqtt://host/home/bedroom/temp

Example publish:

curl -d 75 mqtt://host/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 the payload.

Caveats

Remaining limitations:

Only QoS level 0 is implemented for publish
No way to set retain flag for publish
No TLS (mqtts) support
Naive EAGAIN handling will not handle split messages