WebSocket endpoint creation in FastAPI - Mini Project: Build & Apply

WebSocket endpoint creation

📖 Scenario: You are building a simple chat server using FastAPI. Users will connect to your server using WebSocket to send and receive messages in real time.

🎯 Goal: Create a WebSocket endpoint in FastAPI that accepts connections and echoes back any message sent by the client.

📋 What You'll Learn

Create a FastAPI app instance named app

Create a WebSocket endpoint at path /ws

Accept WebSocket connections using the websocket parameter

Accept and receive text messages from the client

Send back the same message to the client (echo)

Properly accept and close the WebSocket connection

💡 Why This Matters

🌍 Real World

WebSocket endpoints are used in real-time applications like chat apps, live notifications, and online games where instant communication is needed.

💼 Career

Knowing how to create WebSocket endpoints with FastAPI is valuable for backend developers working on interactive web applications requiring real-time data exchange.

1

Create FastAPI app instance

Import FastAPI from fastapi and create an app instance called app.

FastAPI

from fastapi import FastAPI

# Create FastAPI app instance called app
# Your code here

Need a hint?

Use app = FastAPI() to create the app instance.

2

Import WebSocket and create endpoint

Import WebSocket from fastapi. Create a WebSocket endpoint at path /ws using @app.websocket("/ws") and define an async function websocket_endpoint that accepts a parameter named websocket of type WebSocket.

FastAPI

from fastapi import FastAPI, WebSocket

app = FastAPI()

# Create WebSocket endpoint at /ws
# Your code here

Need a hint?

Use @app.websocket("/ws") decorator and define an async function with websocket: WebSocket parameter.

3

Accept connection and receive message

Inside websocket_endpoint, accept the WebSocket connection using await websocket.accept(). Then receive a text message from the client using await websocket.receive_text() and store it in a variable called data.

FastAPI

from fastapi import FastAPI, WebSocket

app = FastAPI()

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    # Accept the connection
    # Receive a text message and store in data
    # Your code here

Need a hint?

Use await websocket.accept() to accept connection and data = await websocket.receive_text() to get the message.

4

Send echo message and close connection

Send back the received message stored in data to the client using await websocket.send_text(data). Then close the WebSocket connection with await websocket.close().

FastAPI

from fastapi import FastAPI, WebSocket

app = FastAPI()

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    data = await websocket.receive_text()
    # Send back the message
    # Close the connection
    # Your code here

Need a hint?

Use await websocket.send_text(data) to send the message and await websocket.close() to close connection.