To help you get started, we've collected the most common ways that websockets is being used within popular public projects.

pyrates / roll / tests / test_websockets_failure.py View on Github

async def test_websocket_failure_receive(liveclient):

    @liveclient.app.route('/failure', protocol="websocket")
    async def failme(request, ws):
        raise NotImplementedError('OUCH')

    websocket = await websockets.connect(liveclient.wsl + '/failure')
    with pytest.raises(websockets.exceptions.ConnectionClosed):
        # Receiving, on the other hand, will raise immediatly an
        # error as the reader is closed. Only the writer is opened
        # as we are expected to send back the closing frame.
        await websocket.recv()

    await websocket.close()
    assert websocket.state == websockets.protocol.State.CLOSED
    assert websocket.close_code == 1011
    assert websocket.close_reason == 'Handler died prematurely.'

View more ways to use websockets

What is websockets?

websockets is a library for building WebSocket servers and clients in Python with a focus on correctness, simplicity, robustness, and performance.

Built on top of asyncio, Python's standard asynchronous I/O framework, the default implementation provides an elegant coroutine-based API.

An implementation on top of threading and a Sans-I/O implementation are also available.

Documentation is available on Read the Docs.

Here's an echo server with the asyncio API:

#!/usr/bin/env python

import asyncio
from websockets.server import serve

async def echo(websocket):
    async for message in websocket:
        await websocket.send(message)

async def main():
    async with serve(echo, "localhost", 8765):
        await asyncio.get_running_loop().create_future()  # run forever

asyncio.run(main())

Here's how a client sends and receives messages with the threading API:

#!/usr/bin/env python

from websockets.sync.client import connect

def hello():
    with connect("ws://localhost:8765") as websocket:
        websocket.send("Hello world!")
        message = websocket.recv()
        print(f"Received: {message}")

hello()

Does that look good?

Get started with the tutorial!

Why should I use websockets?

The development of websockets is shaped by four principles:

1. Correctness: websockets is heavily tested for compliance with 6455. Continuous integration fails under 100% branch coverage.
2. Simplicity: all you need to understand is msg = await ws.recv() and await ws.send(msg). websockets takes care of managing connections so you can focus on your application.
3. Robustness: websockets is built for production. For example, it was the only library to handle backpressure correctly before the issue became widely known in the Python community.
4. Performance: memory usage is optimized and configurable. A C extension accelerates expensive operations. It's pre-compiled for Linux, macOS and Windows and packaged in the wheel format for each system and Python version.

Documentation is a first class concern in the project. Head over to Read the Docs and see for yourself.

Why shouldn't I use websockets?

• If you prefer callbacks over coroutines: websockets was created to provide the best coroutine-based API to manage WebSocket connections in Python. Pick another library for a callback-based API.

• If you're looking for a mixed HTTP / WebSocket library: websockets aims at being an excellent implementation of 6455: The WebSocket Protocol and 7692: Compression Extensions for WebSocket. Its support for HTTP is minimal — just enough for an HTTP health check.

  If you want to do both in the same server, look at HTTP frameworks that build on top of websockets to support WebSocket connections, like Sanic.

What else?

Bug reports, patches and suggestions are welcome!

To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.

For anything else, please open an issue or send a pull request.

Participants must uphold the Contributor Covenant code of conduct.

websockets is released under the BSD license.