title: Azure bot framework - Connection open and close
body: <p>I am new to Azure bot services. I have created a bot and hosted locally. I want to know when the connectivity between user and bot gets closed. 
  I actually need this to store chat history to DB that too before connection getting closed. 
  I am using Directline API. 
  Is bot connection will remains for a long time?
  Is there any event triggers before connection close? 
  How actally connection between use and bot created and closed?</p>