async-websockets

About

asyncws is a library for developing coroutine based websocket applications in Python 3.

It implements RFC 6455, passes the Autobahn Testsuite and supports SSL/TSL out of the box. Based on PEP 3156 and coroutines it makes it easy to write highly concurrent websocket based applications.

Installation

To install the package: python3 setup.py install

API Documentation

Refer to [API Documentation](https://async-websockets.readthedocs.io/) for more information.

Example

Echo server:

import asyncio
import asyncws

@asyncio.coroutine
def echo(websocket):
    while True:
        frame = yield from websocket.recv()
        if frame is None:
            break
        yield from websocket.send(frame)


loop = asyncio.get_event_loop()
server = loop.run_until_complete(
    asyncws.start_server(echo, '127.0.0.1', 8000))
try:
    loop.run_forever()
except KeyboardInterrupt as e:
    server.close()
    loop.run_until_complete(server.wait_closed())
finally:
    loop.close()

Corresponding echo client:

import asyncio
import asyncws

@asyncio.coroutine
def echo(websocket):
    while True:
        yield from websocket.send('hello')
        msg = yield from websocket.recv()
        if msg is None:
            break
        print(msg)


loop = asyncio.get_event_loop()
websocket = loop.run_until_complete(
    asyncws.connect('ws://localhost:8000'))
try:
    loop.run_until_complete(echo(websocket))
except KeyboardInterrupt as e:
    loop.run_until_complete(websocket.close())
    loop.run_until_complete(websocket.wait_closed())
finally:
    loop.close()

SSL/TSL Example

The first step is to create the certificate and key files. A self-signed certificate can be created with a command like:

openssl req -newkey rsa:2048 -nodes -keyout example.key -x509 -days 365 -out example.crt

Create an SSLContext with the certificate and key just generated and then pass the context to start_server():

import asyncio
import asyncws
import ssl

@asyncio.coroutine
def echo(websocket):
    while True:
        frame = yield from websocket.recv()
        if frame is None:
            break
        yield from websocket.send(frame)


ssl_context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
ssl_context.check_hostname = False
ssl_context.load_cert_chain('example.crt', 'example.key')

loop = asyncio.get_event_loop()
loop.set_debug(True)
server = loop.run_until_complete(
    asyncws.start_server(echo, '127.0.0.1', 8000, ssl=ssl_context))
try:
    loop.run_forever()
except KeyboardInterrupt as e:
    server.close()
    loop.run_until_complete(server.wait_closed())
finally:
    loop.close()

An SSLContext is needed to secure the client-side of the socket:

import asyncio
import asyncws
import ssl

@asyncio.coroutine
def echo(websocket):
    while True:
        yield from websocket.send('hello')
        echo = yield from websocket.recv()
        if echo is None:
            break
        print(echo)


ssl_context = ssl.create_default_context(ssl.Purpose.SERVER_AUTH)
ssl_context.check_hostname = False
ssl_context.verify_mode = ssl.CERT_NONE
ssl_context.load_verify_locations('example.crt')

loop = asyncio.get_event_loop()
websocket = loop.run_until_complete(
    asyncws.connect('wss://localhost:8000', ssl=ssl_context))
try:
    loop.run_until_complete(echo(websocket))
except KeyboardInterrupt as e:
    loop.run_until_complete(websocket.close())
    loop.run_until_complete(websocket.wait_closed())
finally:
    loop.close()

Now you have a fully encrypted websocket connection!