WebSockets in FastAPI

What are WebSockets?

WebSockets allow a client and server to talk to each other continuously.

Normally, with HTTP, the client asks the server for something, and the server sends a response.

With WebSockets, the connection stays open, so both sides can send messages whenever they want.

Simple Example

Think of a phone call:

• HTTP → You call, ask a question, get an answer, and the conversation ends.
• WebSocket → You stay on the call and both people can talk anytime.

Why use WebSockets?

WebSockets are useful when we need real-time updates, such as:

•  Chat applications
• Online games
• Live dashboards
• Notifications
• Live location tracking
• Real-time stock prices

WebSockets in FastAPI

FastAPI makes WebSockets easy to create.

from fastapi import FastAPI, WebSocket

app = FastAPI()

@app.websocket("/ws")
async def websocket(websocket: WebSocket):
    await websocket.accept()

    while True:
        message = await websocket.receive_text()
        await websocket.send_text(f"You said: {message}")

What happens here?

1. The client connects to websocket
2. accept() accepts the connection.
3. The server waits for a message.
4. receive_text() receives the message.
5. send_text() sends a response.
6. The connection stays open because of the while true loop.

HTTP vs WebSocket

Simple Example

Imagine a chat app.

When you send "Hello", the server immediately receives it and can send back "Hello!" without creating a new connection every time.

In short

WebSocket = a permanent connection between the client and server for real-time communication.