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: - No username support - Only QoS level 0 is implemented for publish - No way to set retain flag for publish - No username/password support - No TLS (mqtts) support - Naive EAGAIN handling won't handle split messages