Devtools wont work on debugger, works on local server

If i go into `http://localhost:8081/debugger-ui/` the monitor does not do anything (no state, no actions dispatches), but if i go `http://localhost:8000/` everything works fine.

There are logs in the debugger indicating something
```
Console was cleared
23:55:58.746 Running application with appParams: {"rootTag":91}. __DEV__ === true, development-level warning are ON, performance optimizations are OFF
23:55:59.736 connected to remotedev-server
23:57:03.968 WebSocket connection to 'ws://localhost:8081/socketcluster/' failed: WebSocket is closed before the connection is established.
23:58:23.968 WebSocket connection to 'ws://localhost:8081/socketcluster/' failed: WebSocket is closed before the connection is established
```

Is there a way to debug this problem?

I also need to manually especify the default port and hostname, otherwise the server at `http://localhost:8000/` won't work
`remotedev-debugger --hostname localhost --port 8000 --injectserver`

Reproduce the issue by opening http://localhost:8081/debugger-ui/ and running remotedev-debugger --hostname localhost --port 8000 --injectserver. Start with the reported WebSocket failures for /socketcluster/ and compare them with the working localhost:8000 behavior. Done means the debugger monitor shows state and dispatched actions without the connection errors.

Written by the indexing model from the issue text.