title: Is the callback functionality of SocketIO a feature exclusive to SocketIO? And if so, how is the header formed?
body: <p>I'm creating a native mobile project that will use SocketIO on NodeJS as the communications API.</p>
  
  <p>We would like to use the callback functionality of SocketIO, but on native iOS (or Android).</p>
  
  <p>However, the callback functionality doesn't appear in any client implementation of WebSockets that I've found so I am guessing it is a feature exclusive to SocketIO?</p>
  
  <p>If so, what is the header information before the payload that socketIO uses to make this possible.</p>
  
  <p>Over the wire I can see some binary before the JSON payload, but I'm not enough of a JS guru to analyse how the callback functionality on the client side is done, so that I can replicate that in ObjC and Java.</p>