c9.io - how to find the host address to make a mysql connection in node.js platform

I am trying to host my node.js app in Cloud 9 Server. In order to make a mysql connection, I need to know the host address.

This page says in a very absurd (I think I am right ) way :

Hostname    $IP     The same local IP as the application you run on Cloud9

But where do I get the local IP from ? Nowhere in the docs I found it. Any idea ?

EDIT : I used 127.0.0.1 , 0.0.0.0( from echo $IP in the terminal as suggested in an answer) and the values from hostname -I and curl curlmyip.com in the terminal. 4 different IP addresses. None worked.