title: What's the difference between engine.io and socket.io?
body: <p>Please correct me if this question is a duplicate.
  Regarding node.js, I'm using socket.io for real-time socket connection from the client application to the server application.
  I just heard about engine.io, is engine.io a replacement for socket.io?
  I could not find any useful information on engine.io website</p>
  
  <p>Thanks in advance</p>