Eclipse Amlen™ Broker
Eclipse Amlen™ is a scalable, secure, easy to use message broker that can be used for IoT, web and mobile use-cases. It primarily supports the MQTT protocol (v5 and v3.x) but supports JMS and custom protocols as well.
Eclipse Amlen™ is based on an initial contribution of the IBM WIoTP Message Gateway broker so it is a mature, production-ready codebase used by a wide variety of companies and organisations.