Centrifugo

A real-time messaging server that pushes events to browsers and apps over WebSockets and other transports, so you do not have to write the fan-out logic yourself. Delivery is organized into channels and namespaces with per-channel permissions, and it can track online presence and keep recent message history so clients reconnect and catch up.

Teams use it for chat, live dashboards, notifications, order updates and any feed that has to feel instant.

Run on your own infrastructure and events never leave your network, there is no per-connection charge from a hosted broker, and you can put your own authentication in front of it and use a Redis engine for multi-node delivery.