Server disconnected while attempting read with async client

[dev-zero]

This initially started as an issue report here: ol-iver/denonavr#215

Some digging led me to the following minimal reproducers:

import httpx
r = httpx.get('http://192.168.179.35:8080/goform/Deviceinfo.xml')
print(r)

import httpx
import asyncio

async def main():
    async with httpx.AsyncClient() as client:
        r = await client.get('http://192.168.179.35:8080/goform/Deviceinfo.xml')

    print(r)

asyncio.run(main())

Running them gives me:

$ python httpx_sync_get.py 
<Response [200 OK]>
$ $ python httpx_async_get.py 
Traceback (most recent call last):
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_transports/default.py", line 61, in map_httpcore_exceptions
    yield
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_transports/default.py", line 201, in __aiter__
    async for part in self._httpcore_stream:
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpcore/_async/connection_pool.py", line 57, in __aiter__
    async for chunk in self.stream:
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpcore/_bytestreams.py", line 91, in __aiter__
    async for chunk in self._aiterator:
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpcore/_async/http11.py", line 208, in _receive_response_data
    event = await self._receive_event(timeout)
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpcore/_async/http11.py", line 225, in _receive_event
    data = await self.socket.read(self.READ_NUM_BYTES, timeout)
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpcore/_backends/anyio.py", line 65, in read
    raise ReadError("Server disconnected while attempting read") from None
httpcore.ReadError: Server disconnected while attempting read

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/home/tiziano/work/tests/python/denon/httpx_get.py", line 11, in <module>
    asyncio.run(main())
  File "/usr/lib/python3.9/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.9/asyncio/base_events.py", line 642, in run_until_complete
    return future.result()
  File "/home/tiziano/work/tests/python/denon/httpx_get.py", line 7, in main
    r = await client.get('http://192.168.179.35:8080/goform/Deviceinfo.xml')
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_client.py", line 1661, in get
    return await self.request(
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_client.py", line 1425, in request
    response = await self.send(
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_client.py", line 1528, in send
    raise exc
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_client.py", line 1519, in send
    await response.aread()
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_models.py", line 1561, in aread
    self._content = b"".join([part async for part in self.aiter_bytes()])
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_models.py", line 1561, in <listcomp>
    self._content = b"".join([part async for part in self.aiter_bytes()])
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_models.py", line 1577, in aiter_bytes
    async for raw_bytes in self.aiter_raw():
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_models.py", line 1631, in aiter_raw
    async for raw_stream_bytes in self.stream:
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_client.py", line 127, in __aiter__
    async for chunk in self._stream:
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_transports/default.py", line 202, in __aiter__
    yield part
  File "/usr/lib/python3.9/contextlib.py", line 135, in __exit__
    self.gen.throw(type, value, traceback)
  File "/home/tiziano/.local/lib/python3.9/site-packages/httpx/_transports/default.py", line 78, in map_httpcore_exceptions
    raise mapped_exc(message) from exc
httpx.ReadError: Server disconnected while attempting read

• httpx 0.18.1
• python 3.9.5

$ curl -sv http://192.168.179.35:8080/goform/Deviceinfo.xml
*   Trying 192.168.179.35:8080...
* Connected to 192.168.179.35 (192.168.179.35) port 8080 (#0)
> GET /goform/Deviceinfo.xml HTTP/1.1
> Host: 192.168.179.35:8080
> User-Agent: curl/7.77.0
> Accept: */*
> 
* Mark bundle as not supporting multiuse
* HTTP 1.0, assume close after body
< HTTP/1.0 200 OK
< Server: mongoose2.5
< Pragma: no-cache
< Cache-control: no-cache
< Content-Type: text/xml; charset=utf-8
< 
{ [2791 bytes data]
<?xml version="1.0" encoding="utf-8" ?>
<Device_Info>
...

Any ideas?

[tomchristie]

I'm just getting a ConnectTimeout when trying to replicate this?

EDIT: Resolved by httpcore 0.13.6.

[dev-zero]

@tomchristie sorry, the address 192.168.179.35 is my receiver in my local network and I don't feel comfortable setting up a port forward. Since I've been using httpx for my own projects I can confirm that normally the async get works, just not with the webserver built into my AVR (a Denon X1600H) or other Denon receivers as of late: https://community.home-assistant.io/t/denonavr-not-working-since-2021-6-4/315266/19
This issue seems similar to #1174 but there it was the sync get which had some problems.

[dev-zero]

but maybe there is a way I can record the response from that webserver somehow?
On the other hand, it seems that the webserver is speaking HTTP 1.0 according to the returned header...

[tomchristie]

I would make sure you're on the very latest versions of httpx and httpcore.
You could also see if you're getting the same error when running using trio instead of asyncio.

[dev-zero]

Nice, the just released httpcore-0.13.6 solved the issue. Thanks a lot!