CODEWITHSUNDEEP
pythoniiswebsocketreverse-proxyiis-10
afar
afar

Reputation: 165

Python websockets module and IIS as reverse proxy

I run the python websocket server of the websokets module on the localhost:5005. The code from documentation page:

#!/usr/bin/env python

import asyncio
import websockets
import logging

logger = logging.getLogger('websockets')
logger.setLevel(logging.DEBUG)
logger.addHandler(logging.StreamHandler())

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

async def main():
    async with websockets.serve(echo, "localhost", 5005):
        await asyncio.Future()  # run forever

asyncio.run(main())

Clients can access it by connecting to the URL ws://localhost:5005. A sample client code is given in the websockets module documentation page.
The goal is to enable clients to access the server via IIS (Windows native webserver) acting as a reverse proxy, i.e., via the URL ws://localhost/app.

IIS-10 settings:

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <system.webServer>
        <rewrite>
            <rules>
                <rule name="ReverseProxy" stopProcessing="true">
                    <match url="(.*)" />
                    <action type="Rewrite" url="http://localhost:5005" logRewrittenUrl="true" />
                </rule>
            </rules>
        </rewrite>
    </system.webServer>
</configuration>

As soon as a client attempts to connect, it gets disconnected and the server throws this exception:

= connection is CONNECTING
< GET / HTTP/1.1
< Cache-Control: no-cache
< Connection: Upgrade
< Pragma: no-cache
< Upgrade: websocket
< Accept-Encoding: gzip, deflate, br, peerdist
< Accept-Language: en-US,en;q=0.9
< Host: localhost:5005
< Max-Forwards: 10
< User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36
< Origin: null
< Sec-WebSocket-Version: 13
< Sec-WebSocket-Key: /C9ah/z+wAo4mnoACSz2IA==
< Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
< X-Original-URL: /app
< X-Forwarded-For: [::1]:52798
< X-ARR-LOG-ID: 8c59749a-4e5d-43cf-8a5a-c4421cc4ecc8
< X-P2P-PeerDist: Version=1.1
< X-P2P-PeerDistEx: MinContentInformation=1.0, MaxContentInformation=2.0
> HTTP/1.1 101 Switching Protocols
> Upgrade: websocket
> Connection: Upgrade
> Sec-WebSocket-Accept: W9Sttf7fHX3aB9zd4b/PVGt0Ldg=
> Sec-WebSocket-Extensions: permessage-deflate; server_max_window_bits=12; client_max_window_bits=12
> Date: Fri, 15 Jul 2022 19:14:32 GMT
> Server: Python/3.7 websockets/10.3
connection open
= connection is OPEN
! failing connection with code 1006
= connection is CLOSED
x half-closing TCP connection
connection handler failed
Traceback (most recent call last):
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 945, in transfer_data
    message = await self.read_message()
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 1015, in read_message
    frame = await self.read_data_frame(max_size=self.max_size)
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 1090, in read_data_frame
    frame = await self.read_frame(max_size)
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 1149, in read_frame
    extensions=self.extensions,
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\framing.py", line 70, in read
    data = await reader(2)
  File "C:\Program Files\Python37\lib\asyncio\streams.py", line 677, in readexactly
    raise IncompleteReadError(incomplete, n)
asyncio.streams.IncompleteReadError: 0 bytes read on a total of 2 expected bytes
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\server.py", line 232, in handler
    await self.ws_handler(self)
  File "D:/Robotic Framework/RoboticApps/UI_Framework/server.py", line 12, in echo
    async for message in websocket:
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 482, in __aiter__
    yield await self.recv()
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 553, in recv
    await self.ensure_open()
  File "C:\Users\amin.ramezanifar\AppData\Roaming\Python\Python37\site-packages\websockets\legacy\protocol.py", line 921, in ensure_open
    raise self.connection_closed_exc()
websockets.exceptions.ConnectionClosedError: no close frame received or sent
connection closed

To make sure if IIS settings are correct, I used another websocket library named "simple-websocket-server" from here and it worked fine. Also I tried a simple Node.js server from here and it was successful.
What could be wrong?

Upvotes: 1

Views: 1260

Answers (1)

user1468499
user1468499

Reputation: 26

Amin (question author) and I figured out that you have to disable compression in websockets because IIS doesn't support it.

It worked with other libraries because they don't implement compression or don't enable it by default, unlike websockets.

For details, see the discussion on GitHub: https://github.com/aaugustin/websockets/issues/1192

Upvotes: 1

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