Realtime Socket Framework

This open-source real-time communication library for Node.js and the browser was created by Guillermo Rauch, the founder and chief executive officer of Vercel, in 2010, providing a reliable, event-based, bi-directional communication layer built on top of the WebSocket protocol with automatic fallback to HTTP long-polling for environments where WebSocket is not available, enabling real-time applications including chat, collaboration, live dashboards, multiplayer games, and push notifications, adopted by Microsoft Teams, Trello, Alibaba, and over three million websites. The reliability features include automatic reconnection with exponential backoff when the connection drops, message buffering during disconnection periods to ensure no messages are lost, packet acknowledgement for request-response patterns over the connection, and timeout handling for unresponsive connections, providing a communication layer that gracefully handles network instability, mobile network switching, and server restarts without developer intervention. The rooms and namespaces feature enables broadcasting messages to subsets of connected clients, with rooms for grouping clients by topic, channel, or user role, and namespaces for separating application endpoints on the same server, supporting multi-tenant applications, private messaging, and targeted event delivery without iterating through all connections. The adapter system supports horizontal scaling through Redis, MongoDB, and Postgres adapters, enabling servers to run across multiple processes and machines while maintaining real-time communication between all connected clients. The middleware support for authentication. The binary streaming for file uploads. The administration UI for monitoring. Designed for backend developers building real-time applications.