Websockets in Python

Websockets in Python are used to perform different functions and achieve different goals. Learn more about this aspect of Python here.

Simple Echo with aiohttp

aiohttp provides asynchronous websockets.

Python 3.x Version ≥ 3.5

import asyncio
from aiohttp import ClientSession
with ClientSession() as session:
async def hello_world():
websocket = await session.ws_connect("wss://echo.websocket.org")
websocket.send_str("Hello, world!")
print("Received:", (await websocket.receive()).data)
await websocket.close()
loop = asyncio.get_event_loop()
loop.run_until_complete(hello_world())

Websockets in Python: Wrapper Class with aiohttp

aiohttp.ClientSession may be used as a parent for a custom WebSocket class.

Python 3.x Version ≥ 3.5

import asyncio
from aiohttp import ClientSession
class EchoWebSocket(ClientSession):
URL = "wss://echo.websocket.org"
def init(self):
super().init()
self.websocket = None
async def connect(self):
"""Connect to the WebSocket."""
self.websocket = await self.ws_connect(self.URL)
async def send(self, message):
"""Send a message to the WebSocket."""
assert self.websocket is not None, "You must connect first!"
self.websocket.send_str(message)
print("Sent:", message)
async def receive(self):
"""Receive one message from the WebSocket."""
assert self.websocket is not None, "You must connect first!"
return (await self.websocket.receive()).data
async def read(self):
"""Read messages from the WebSocket."""
assert self.websocket is not None, "You must connect first!"
while self.websocket.receive():
message = await self.receive()
print("Received:", message)
if message == "Echo 9!":
break
async def send(websocket):
for n in range(10):
await websocket.send("Echo {}!".format(n))
await asyncio.sleep(1)
loop = asyncio.get_event_loop()
with EchoWebSocket() as websocket:
loop.run_until_complete(websocket.connect())
tasks = (
send(websocket),
websocket.read()
)
loop.run_until_complete(asyncio.wait(tasks))
loop.close()

Websockets in Python: Using Autobahn as a Websocket Factory

The Autobahn package can be used for Python web socket server factories.

Python Autobahn package documentation

To install, typically one would simply use the terminal command

(For Linux):

sudo pip install autobahn

(For Windows):

python -m pip install autobahn

Then, a simple echo server can be created in a Python script:

from autobahn.asyncio.websocket import WebSocketServerProtocol class MyServerProtocol(WebSocketServerProtocol):
'''When creating server protocol, the
user defined class inheriting the
WebSocketServerProtocol needs to override
the onMessage, onConnect, et-c events for
user specified functionality, these events
define your server's protocol, in essence'''
def onMessage(self,payload,isBinary):
'''The onMessage routine is called
when the server receives a message.
It has the required arguments payload
and the bool isBinary. The payload is the
actual contents of the "message" and isBinary
is simply a flag to let the user know that
the payload contains binary data. I typically
elsewise assume that the payload is a string.
In this example, the payload is returned to sender verbatim.''' self.sendMessage(payload,isBinary)
if__name__=='main':
try:
importasyncio
except ImportError:
'''Trollius = 0.3 was renamed'''
import trollius as asyncio
from autobahn.asyncio.websocketimportWebSocketServerFactory factory=WebSocketServerFactory()
'''Initialize the websocket factory, and set the protocol to the above defined protocol(the class that inherits from autobahn.asyncio.websocket.WebSocketServerProtocol)''' factory.protocol=MyServerProtocol
'''This above line can be thought of as "binding" the methods
onConnect, onMessage, et-c that were described in the MyServerProtocol class
to the server, setting the servers functionality, ie, protocol'''
loop=asyncio.get_event_loop()
coro=loop.create_server(factory,'127.0.0.1',9000)
server=loop.run_until_complete(coro)
'''Run the server in an infinite loop'''
try:
loop.run_forever()
except KeyboardInterrupt:
pass
finally:
server.close()
loop.close()

In this example, a server is being created on the localhost (127.0.0.1) on port 9000. This is the listening IP and port. This is important information, as using this, you could identify your computer’s LAN address and port forward from your modem, though whatever routers you have to the computer. Then, using google to investigate your WAN IP, you could design your website to send WebSocket messages to your WAN IP, on port 9000 (in this example).

It is important that you port forward from your modem back, meaning that if you have routers daisy chained to the modem, enter into the modem’s configuration settings, port forward from the modem to the connected router, and so forth until the final router your computer is connected to is having the information being received on modem port 9000 (in this example) forwarded to it.

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