Glossary

WebSocket

Definition: WebSocket is a communication protocol that provides a persistent, full-duplex channel over a single TCP connection, enabling real-time data exchange between client and server.

The WebSocket protocol (RFC 6455) enables full-duplex, bidirectional communication between a client and a server over a single, long-lived TCP connection. Unlike HTTP, which follows a request–response model (the client always initiates), WebSocket allows both sides to send messages independently at any time after the connection is established.

HTTP Polling vs WebSocket

  • HTTP Short Polling — Client repeatedly sends requests every N seconds asking "anything new?". Wasteful and adds latency.
  • HTTP Long Polling — Client sends a request; the server holds it open until data is available. Better, but still has overhead per message.
  • WebSocket — One handshake, then a persistent connection. Messages flow instantly in both directions with minimal overhead.

WebSocket Handshake

A WebSocket connection starts as an HTTP/1.1 upgrade request:

GET /chat HTTP/1.1
Upgrade: websocket
Connection: Upgrade

The server responds with 101 Switching Protocols and the connection is upgraded.

Use Cases

  • Live chat applications.
  • Real-time dashboards and analytics.
  • Multiplayer browser games.
  • Collaborative editing (Google Docs-style).
  • Financial tickers and live sports scores.
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