WebSockets

WebSockets are a full-duplex communication protocol that allows persistent, bidirectional communication between a client and a server. Unlike HTTP, which follows a request-response model, WebSockets enable real-time interaction without repeatedly polling the server.

Key Features

• Persistent Connection: The connection remains open, reducing overhead.
• Bidirectional Communication: Both the server and client can send messages at any time.
• Low Latency: No need for repeated HTTP requests, making it ideal for real-time apps.
• Uses a Single TCP Connection: Unlike HTTP polling, which repeatedly opens and closes connections.

How they work

1. Handshake: The client initiates a connection with an Upgrade request via HTTP.
2. Connection Upgrade: The server responds with 101 Switching Protocols, upgrading the connection to WebSockets.
3. Persistent Communication: The connection remains open, allowing real-time data exchange.
4. Closure: Either the client or server can close the connection.

Examples

Implementing WebSockets in Python

from fastapi import FastAPI, WebSocket
 
app = FastAPI()
 
@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(f"Message received: {data}")

Run with:

uvicorn myapp:app --host 0.0.0.0 --port 8000

Clients can now connect via WebSockets and send messages.

WebSockets in JavaScript (Client-Side)

const socket = new WebSocket("ws://localhost:8000/ws");
 
socket.onopen = () => {
    console.log("Connected to WebSocket");
    socket.send("Hello Server!");
};
 
socket.onmessage = (event) => {
    console.log("Received:", event.data);
};

This script connects to a WebSocket server, sends a message, and listens for responses.

Security Considerations

• Use WSS (WebSockets over SSL/TLS): Encrypts data to prevent interception.
• Implement Authentication: Use tokens or session validation.
• Rate Limiting: Prevents abuse and DDoS attacks.