In December 2021, I had the chance to write a three-post blog series for HiveMQ. They provide an MQTT compatible message broker you can install yourself, or through a cloud service they provide. That cloud service is free to connect up to 100 devices! Even for the most enthusiastic maker, that’s a lot of microcontrollers or computers!
You can find example code for many programming languages on the HiveMQ site, but as a Java and Raspberry Pi fan, I wanted to add some extra examples. The full descriptions are available on the HiveMQ blog, so let me give you a short overview here on DZone to give you an idea of the possibilities.