Exception in ASGI application - 'NoneType' object is not subscriptable

Hello, I have ‘NoneType’ error on asgi_send method, im not sure for why this happens:

[2018-11-07 22:13:39 -0500] [2868] [ERROR] Exception in ASGI application
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/dist-packages/uvicorn/protocols/websockets/websockets_impl.py", line 140, in run_asgi
    result = await asgi(self.asgi_receive, self.asgi_send)
  File "/usr/local/lib/python3.6/dist-packages/channels/sessions.py", line 175, in __call__
    return await self.inner(receive, self.send)
  File "/usr/local/lib/python3.6/dist-packages/channels/middleware.py", line 41, in coroutine_call
    await inner_instance(receive, send)
  File "/usr/local/lib/python3.6/dist-packages/channels/consumer.py", line 54, in __call__
    await await_many_dispatch([receive, self.channel_receive], self.dispatch)
  File "/usr/local/lib/python3.6/dist-packages/channels/utils.py", line 50, in await_many_dispatch
    await dispatch(result)
  File "/usr/local/lib/python3.6/dist-packages/channels/consumer.py", line 67, in dispatch
    await handler(message)
  File "/usr/local/lib/python3.6/dist-packages/channels/generic/websocket.py", line 173, in websocket_connect
    await self.connect()
  File "/home/deploy/xxxxxx/app/consumers.py", line 314, in connect
    await self.accept()
  File "/usr/local/lib/python3.6/dist-packages/channels/generic/websocket.py", line 186, in accept
    await super().send({"type": "websocket.accept", "subprotocol": subprotocol})
  File "/usr/local/lib/python3.6/dist-packages/channels/consumer.py", line 75, in send
    await self.base_send(message)
  File "/usr/local/lib/python3.6/dist-packages/channels/sessions.py", line 226, in send
    return await self.real_send(message)
  File "/usr/local/lib/python3.6/dist-packages/uvicorn/protocols/websockets/websockets_impl.py", line 170, in asgi_send
    self.scope["server"][0],
TypeError: 'NoneType' object is not subscriptable

Any ideas?

Django==2.1.3 channels==2.1.5 channels_redis==2.3.1 gunicorn==19.9.0 uvicorn==0.3.20

[agronick]

Its really easy to see how this is happening. get_local_addr(transport) returns None if the sockname key is not set. You just follow that code to where it gets set on the scope and its taking [0] from None. What should that function return when sockname is not set (it appears to never be set) instead of None?

[jordaneremieff]

What is a simple means of reproducing the issue in order to debug/test the solution? According to the ASGI spec, the server field is optional and defaults to None. It may be clear what is happening, but we need a way to reproduce the behaviour to determine a generic solution.