title: Be sure iOS application have received data?
body: <p>We have been developing a communication application for <strong>iOS</strong>. 
  We need be sure an application received data <em>(message)</em> by web socket or <strong>push-notification</strong> <em>(I am not a iOS-developer, but as know an application may not received data if it not on top)</em>.</p>
  
  <p>I am backend-developer and I am trying resolve it on server side - duplicate a message if server don't receive confirmation <em>(by API)</em>. However it overly complicated code on the server. I think it's not right way.</p>
  
  <p>Maybe an application must ask server about change state?</p>
  
  <p>I will be glad see all suggestions?</p>
  
  <p>PS: it's not a chat application. Notifications are using for service functions and user notification.</p>