title: can MQTT be used to implement Request / Response behavior
body: <p>We are planning to use MQTT to deliver messages from our server to an android devices 
  we decided to go with the open source server mosquitto.</p>
  
  <p>in most of the cases this is enough.(Publishing / subscribing )
  but we have a cases where the client need to send parameters and get response from the server.
  i know the direct approach is to go with Http (Servlets for example) .
  but can we achieve this using MQTT since it would  mean lower bandwidth consumption to the user ?  </p>