To use MQTT, you need to decide what MQTT broker you will use. You can either select a publicly-available broker, or host your own broker, either in an internal network, or on the Internet. For the purposes of this book, we will use a free, publicly-available MQTT broker, hosted by iot.eclipse.org. It uses the Mosquitto broker(http://mosquitto.org/).
A non-exhaustive list of MQTT broker software is available at https://github.com/mqtt/mqtt.github.io/wiki/servers
. There are many to choose from.
The broker at iot.eclipse.org is publicly accessible, and it allows anonymous access and wildcard subscriptions. Any data you publish will be visible to anybody on the internet. For the purposes of illustrating how MQTT works, ...