Eclipse Mosquitto is an open source (EPL/EDL licensed) message broker that implements the MQTT protocol versions 5.0, 3.1.1 and 3.1. Mosquitto is lightweight and is suitable for use on all devices from low power single board computers to full servers.
The MQTT protocol provides a lightweight method of carrying out messaging using a publish/subscribe model. This makes it suitable for Internet of Things messaging such as with low power sensors or mobile devices such as phones, embedded computers or microcontrollers.
The Mosquitto project also provides a C library for implementing MQTT clients, and the very popular mosquitto_pub and mosquitto_sub command line MQTT clients.
Mosquitto is highly portable and available for a wide range of platforms. Go to the dedicated download page to find the source or binaries for your platform.
Read the Change Log to find out about recent releases.
You can have your own instance of Mosquitto running in minutes, but to make testing even easier, the Mosquitto Project runs a test server at test.mosquitto.org where you can test your clients in a variety of ways: plain MQTT, MQTT over TLS, MQTT over TLS (with client certificate, MQTT over WebSockets and MQTT over WebSockets with TLS.platforms.
Use the security page to find out how to report vulnerabilities or responses to past security issues.