Review on Eclipse Mosquitto by Dan Chunn

It's open source, it supports multiple protocols and has good documentation. The broker could be configured easier, but I like the way it is right now. I used Mosquitto with Raspberry Pi as an IoT gateway that publishes sensor data to other systems (Web, mobile phone). I like that it has some great features, such as support for encryption (which helps secure data), SSL/TLS connections, authentication methods, etc. It's not bad at all - but maybe there are better options out there? We needed something with an easy-to-use API / SDK so we could integrate into our apps easily without having to write code ourselves. The fact that they offer free versions makes this even more appealing!