title: Android real time notification
body: <p>I'm developing a payment app that will use QR Code. The customer will show his personal QR Code and the merchant will read the QR Code, enter the value of the purchase and send the information for a webservice. So the customer will be notified about the purchase, and will authorize.</p>
  
  <p>My question is about the notification abouth the purchase for the customer. What is the best approach? I think use Timer, so the customer app will consult a webservice each 10 seconds to check if there are a new notification. But its probably the customer make just one purchase per day (or week!) with the app. So I think that a http request each 10 seconds its much requests for the necessity. By other way, the customer need receive the notification like real time to finish the purchase.</p>
  
  <p>The is another approach for this function? Can I my webservice send a notification for the customer app when it receive the purchase request from the merchant?</p>
  
  <p>I think what I want is the same mechanism that apps like Tinder or Badoo use, when the user receive a notification when he have a match.</p>