FastAPI Backend Development Bootcamp · Aula

Implementando WebSockets no FastAPI

Aprenda a adicionar endpoints WebSocket à sua aplicação FastAPI e a gerenciar conexões.

Implementando WebSockets no FastAPI é uma aula grátis de FastAPI Backend Development Bootcamp no CoddyKit. Esta é a aula 2 de 4. Você pode ler a aula completa abaixo gratuitamente — depois pratica ao vivo no navegador com um editor de código integrado e um tutor de IA 24/7. Faz parte do caminho de aprendizado de FastAPI Backend Development Bootcamp, e seu progresso é sincronizado entre a web e o app CoddyKit. O curso de FastAPI Backend Development Bootcamp inclui 4 aulas no total.

Partes desta aula ainda não foram traduzidas e aparecem em inglês.

Real-time with FastAPI WebSockets

Welcome to implementing WebSockets with FastAPI! WebSockets provide a persistent, full-duplex communication channel between a client and a server.

Full-duplex: Both client and server can send and receive messages simultaneously.
Real-time: Ideal for applications needing instant updates, like chat, live dashboards, or gaming.

FastAPI has excellent built-in support for WebSockets, leveraging Python's async/await features.

Defining a WebSocket Endpoint

Just like HTTP endpoints, you define WebSocket endpoints using a decorator. Instead of @app.get() or @app.post(), you use @app.websocket().

Your endpoint function must be async def and accept a websocket: WebSocket parameter. This WebSocket object is your primary tool for interaction.

The first step inside your function is always to await websocket.accept() to establish the connection.

Your First WebSocket Connection

Let's create our first WebSocket endpoint. This simple example accepts a connection, sends a welcome message, and then closes the connection.

Notice the @app.websocket("/ws") decorator and the async def function, which are key for WebSocket handling.

Try running this example and observe the connection:

from fastapi import FastAPI, WebSocket

app = FastAPI()

@app.websocket("/ws")
async def websocket_endpoint(websocket: WebSocket):
    await websocket.accept()
    await websocket.send_text("Welcome! Connection established.")
    await websocket.close()

Handling WebSocket Disconnections

WebSocket connections can be interrupted for various reasons (client closes tab, network error). It's crucial to handle these disconnections gracefully.

FastAPI raises a WebSocketDisconnect exception when a client disconnects. You can catch this exception to perform cleanup tasks, like removing the client from a list of active connections.

Wrap your WebSocket communication logic in a try...except WebSocketDisconnect block.

Receiving Messages from Clients

Once connected, your server can receive messages from the client. The WebSocket object provides methods for this:

await websocket.receive_text(): For receiving string data.
await websocket.receive_bytes(): For receiving binary data.
await websocket.receive_json(): For receiving JSON data (requires python-multipart).

These operations are asynchronous, so always use await.

Echoing Client Messages Back

This example demonstrates a simple 'echo' server. It accepts a connection, then continuously receives messages from the client and sends them back.

The while True loop keeps the connection open, and the try...except WebSocketDisconnect handles when the client leaves.

from fastapi import FastAPI, WebSocket, WebSocketDisconnect

app = FastAPI()

@app.websocket("/ws/echo")
async def websocket_echo(websocket: WebSocket):
    await websocket.accept()
    try:
        while True:
            data = await websocket.receive_text()
            print(f"Received from client: {data}")
            await websocket.send_text(f"Server echoed: {data}")
    except WebSocketDisconnect:
        print("Client disconnected.")

Sending Messages to Clients

Similarly, your server can send messages to the client. The WebSocket object offers:

await websocket.send_text("your message"): To send string data.
await websocket.send_bytes(b"your bytes"): To send binary data.
await websocket.send_json({"key": "value"}): To send JSON data.

Remember to await these calls. It's common to send a response right after receiving a message.

Working with JSON Data

For structured data, sending and receiving JSON is preferred. FastAPI's WebSocket object handles serialization/deserialization for you.

Sending: Pass a Python dict to send_json().
Receiving: receive_json() returns a Python dict.

This simplifies data exchange compared to manually parsing strings.

Simple Connection Manager

For applications with multiple clients, you'll need to manage active connections. A common pattern is to use a class to keep track of all connected WebSocket objects.

This manager can then be used to add/remove connections and send messages to specific clients or broadcast to all.

from fastapi import WebSocket

class ConnectionManager:
    def __init__(self):
        self.active_connections: list[WebSocket] = []

    async def connect(self, websocket: WebSocket):
        await websocket.accept()
        self.active_connections.append(websocket)

    def disconnect(self, websocket: WebSocket):
        self.active_connections.remove(websocket)

    async def send_personal_message(self, message: str, websocket: WebSocket):
        await websocket.send_text(message)

# In a real app, you'd integrate 'manager' into your FastAPI endpoint
manager = ConnectionManager()

WebSocket Interaction Check

You've learned the basics of setting up and interacting with WebSocket connections in FastAPI.

Let's check your understanding of accepting new connections.

Recap: Implementing WebSockets

You've successfully learned how to implement WebSockets in FastAPI!

Use @app.websocket() to define endpoints.
Always await websocket.accept() to establish the connection.
Handle disconnections with try...except WebSocketDisconnect.
Use await websocket.receive_text() and await websocket.send_text() for communication.
For structured data, send_json() and receive_json() are your friends.

Next, you'll build a real-time chat application to put these concepts into practice!

Perguntas Frequentes

A aula “Implementando WebSockets no FastAPI” é grátis?

Sim — o texto completo de “Implementando WebSockets no FastAPI” é grátis para ler aqui na web. Para praticá-la interativamente (um editor de código integrado e um tutor de IA 24/7) e desbloquear o restante do curso de FastAPI Backend Development Bootcamp, atualize para CoddyKit PRO. O curso de FastAPI Backend Development Bootcamp inclui 4 aulas no total.

O que vou aprender em “Implementando WebSockets no FastAPI”?

Aprenda a adicionar endpoints WebSocket à sua aplicação FastAPI e a gerenciar conexões. Você pratica FastAPI Backend Development Bootcamp com código prático que executa diretamente no navegador, e um tutor de IA 24/7 responde suas dúvidas enquanto trabalha na aula.

Preciso ter experiência prévia para começar FastAPI Backend Development Bootcamp?

Nenhuma experiência prévia é necessária. FastAPI Backend Development Bootcamp no CoddyKit é estruturado para alunos iniciantes até avançados, então você pode começar aqui ou desde o início e aprender no seu ritmo. Esta é a aula 2 de 4.

Quanto tempo leva a aula “Implementando WebSockets no FastAPI”?

A maioria das aulas CoddyKit leva cerca de 5–10 minutos. Cada uma é compacta e interativa, então você faz progresso constante e retoma exatamente de onde parou entre web e app.

Posso escrever e executar código nesta aula de FastAPI Backend Development Bootcamp?

Sim. Cada aula de FastAPI Backend Development Bootcamp inclui um editor de código integrado, então você escreve e executa código real direto no navegador e recebe feedback de IA instantaneamente — nenhuma configuração local necessária.

Todas as aulas deste curso

Fundamentos do protocolo WebSocket
Implementando WebSockets no FastAPI
Criando uma aplicação de chat em tempo real
Escalonamento de WebSockets com um backplane Pub/Sub

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