Tutorial 1: Implementing Websockets in FastAPI using Python

In this tutorial, we will be covering how to create a basic WebSocket server using FastAPI in Python. FastAPI is a modern web framework for building APIs with Python and it comes with WebSocket support out of the box. WebSockets allow bidirectional communication between a client and a server in real time, making them perfect for applications that require continuous updating of data.

To get started, make sure you have FastAPI installed. You can install FastAPI and the Uvicorn ASGI server with the following command:

pip install fastapi uvicorn

Next, let’s create a new Python file for our WebSocket server. You can name it app.py or any other name you prefer. In this file, we will define our FastAPI application and include the WebSocket route.

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 text was: {data}")

In the code above, we have defined a new route /ws that will handle WebSocket connections. When a client connects to this route, the websocket_endpoint function is called. Inside this function, we use the accept method to establish the WebSocket connection with the client.

We then enter a while loop to continuously receive messages from the client using the receive_text method. We can then process the data and send a response back to the client using the send_text method.

To run our WebSocket server, we need to start the FastAPI application using Uvicorn. You can start the server with the following command:

uvicorn app:app --reload

Now that our server is running, we can test our WebSocket endpoint with a WebSocket client. You can use tools like Postman, wscat, or any WebSocket client library to connect to the server.

For example, using wscat, you can connect to your WebSocket server with the following command:

wscat -c ws://localhost:8000/ws

Once connected, you can send messages to the server and receive responses back. The server will echo back the message sent by the client with a prefix "Message text was: ".

And that’s it! You have successfully created a WebSocket server using FastAPI in Python. You can further extend this server to include more complex functionality such as broadcasting messages to multiple clients or handling different types of messages. FastAPI’s WebSocket support makes it easy to build real-time applications with minimal effort. I hope you found this tutorial helpful and have fun experimenting with WebSocket connections in FastAPI!