WebSocket is a communication protocol defined in RFC 6455 that enables full-duplex, bidirectional communication over a single TCP connection. Unlike HTTP's request-response model, WebSocket maintains a persistent connection where both client and server can push messages independently, making it ideal for real-time applications like chat systems, live dashboards, collaborative editing, and multiplayer gaming. The protocol starts with an HTTP upgrade handshake, transitions to a framing-based message exchange, and remains open until explicitly closed. One key consideration: WebSocket connections are stateful and long-lived, requiring careful design for scalability, authentication, reconnection, and resource management — especially when handling thousands of concurrent connections across distributed servers.