Why is WebSocket needed if HTTP exists? What is the main difference?

WebSocket is needed for bidirectional persistent communication between the client and server, whereas HTTP is a request-response protocol where the client initiates each request.

Main difference:

• HTTP: the client sends a request, the server responds, and the connection is closed.
• WebSocket: a persistent connection is established, over which both parties can send data at any time.

This is important for real-time applications, such as chats, games, financial trading platforms.

Example in Python using the websockets library:

import asyncio
import websockets

async def echo(websocket, path):
    async for message in websocket:
        await websocket.send(f"Echo: {message}")

asyncio.get_event_loop().run_until_complete(
    websockets.serve(echo, 'localhost', 8765))
asyncio.get_event_loop().run_forever()