IPython notebook connection failed issue

Question

This is probably very simple; and I am embarrassed to ask; but I spent a long time trying to solve it already. I am trying to use an IPython notebook and on the click to get a Python 3 notebook, I often (but not always) get:

Connection failed

A connection to the notebook server could not be established. The notebook will continue trying to connect, but until it does, you will NOT be able to run code. Check your network connection or notebook server connection."

The obvious answer might appear that I have no internet connection; but I can access the internet and interact with external websites. It seems to be a problem of connecting with something local to my computer.

The really frustrating part is that sometimes in the past this has worked with no problem. That suggests to me that it is a simple setting issue. Does anyone have suggestions about how I can debug this?

My operating system is Windows (both 7, and 8.1). I am also using Anaconda 2.3 and Python 3.4

Answer 1

Downgrade Tornado to 5.1.1 from 6.0, that will solve it.
Apparently, Tornado 6.0 breaks notebook.