PeerJS Server is a Node.js application that facilitates WebRTC peer-to-peer connections by handling signaling between clients. It does not proxy media data but exchanges metadata (offers, answers, ICE candidates) via WebSocket connections. The server provides an HTTP API for obtaining client IDs and discovering peers (when enabled), manages client state and message queues for offline clients, and includes services to monitor connection health and expire stale messages. Built with Express.js and the 'ws' library, it features a modular architecture separating API routing, message handling, core logic (realm/model management), and background services (connection checking, message expiration). The CLI entry point allows running as a standalone server, while the programmatic API enables integration into existing Node.js applications.