ejabberd

The software provides a real‑time communication platform built on Erlang/OTP that implements the XMPP protocol while also offering MQTT broker and SIP gateway functionality. It can be deployed on‑premises or in containers, and supports clustering for fault‑tolerance and massive scalability, handling millions of concurrent connections with consistent‑hash routing and reduced memory overhead. Administration is performed through a command‑line tool and a REST API, and the system includes hooks for extensive customization to suit use cases such as mobile messaging, gaming, or IoT.

Typical users are developers and operators who need a self‑hosted, open‑source solution for instant messaging, publish‑subscribe, or voice over IP services. The platform’s modular design allows integration with mobile libraries (XMPPFramework, Smack, Retrofit), web libraries (Strophe with WebSocket/BOSH), and other services via the built‑in command line interface.

Distinctive aspects include the combination of three protocols in a single server, native clustering with active‑active nodes, and the ability to upgrade without downtime while guaranteeing message delivery acknowledgments. The project is released under GPL‑2.0, maintained by ProcessOne, and provides documentation, translation support, and Docker images for easy installation.