Socket.IO Redis Adapter

Redis-based adapter for Socket.IO that enables broadcasting events between multiple Socket.IO server instances via Redis Pub/Sub. Version 8.4.6 (stable), maintained by the Socket.IO team. Ships TypeScript types. Requires socket.io-adapter ^2.4.0 peer dependency. Supports CommonJS, ES modules, and TypeScript. Key differentiator: uses two separate Redis clients (pub/sub) for reliability; supports both standard and sharded Pub/Sub (Redis 7.0+). Migration from legacy socket.io-redis package requires API changes.