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WebSockets Overview

WebSockets provide a full-duplex communication channel over a single, long-lived connection between client and server. Unlike HTTP, which is request/response-based, WebSockets enable real-time data transfer without repeated polling.

This page introduces WebSockets, their advantages, and how they fit into modern backend systems.

🔄 What is a WebSocket?

A WebSocket is a persistent connection between a client (e.g., browser or mobile app) and server, established through a single HTTP handshake and upgraded to a TCP-based protocol. Once connected, either party can send data at any time.

Key properties:

  • Full-duplex: Both client and server can communicate simultaneously.
  • Low latency: Ideal for real-time features like chat, notifications, games, or live dashboards.
  • Persistent: The connection remains open, reducing handshake overhead.

✅ Why Use WebSockets?

Use Case Description
Chat applications Real-time message delivery and status updates
Live notifications Push alerts to users instantly
Online gaming Low-latency interactions between players
Collaborative tools Shared state updates (e.g., whiteboards, code editors)
IoT dashboards Stream data from sensors in real-time

🔧 How It Works

  1. Client initiates a connection with a special HTTP request:
GET /ws HTTP/1.1
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw==
  1. Server responds with a status indicating a successful upgrade:
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
  1. Communication begins over the new WebSocket protocol.

Both the client and server can now send JSON, binary, or text data over the connection.

📚 Common Backend Implementations

Framework WebSocket Support
FastAPI Native via WebSocket and async endpoints
Django Via Channels and ASGI
Node.js With ws, socket.io, or uWebSockets.js
Go Via gorilla/websocket or nhooyr.io/websocket
Rust Libraries like tokio-tungstenite or warp

📦 Protocol Design (High-Level)

While WebSocket is a transport protocol, you typically define your application-level protocol over it.

Example message format:

{
  "event": "join_room",
  "data": {
    "room_id": "abc123",
    "user_id": "user789"
  }
}

This allows you to structure interactions as event-based messages (see Message Format).

🚨 Limitations

  • Requires fallback support if WebSockets are blocked (e.g., corporate firewalls)
  • Connection management is more complex (e.g., reconnection, heartbeat, scaling)
  • No built-in message delivery guarantees (you must handle retries/acks)

🔚 Next Steps

Explore the following sections to learn how to structure, secure, and integrate WebSockets: