websockets

Centrifugo is an open-source scalable real-time messaging server that can instantly deliver messages to application users over WebSocket, HTTP-streaming, SSE, GRPC, and WebTransport. It provides a language-agnostic PUB/SUB server for building real-time applications.

AnyCable is a realtime server for two-way reliable communication over WebSockets and SSE. It provides a scalable and performant solution for adding realtime features to any backend application.