What is the disadvantage of using websocket/socket.io where ajax will do?

Question

Similar questions have been asked before and they all reached the conclusion that AJAX will not become obsolete. But in what ways is ajax better than websockets?

Wit

Answer 1

If you want the connection to server open and if continuous polling to the server will be there then go for sockets else you are good to go with ajax.

Simple Analogy : Ajax asks questions(requests) to server and server gives answers(responses) to these questions. Now if you want to ask continuous questions then ajax wont work, it has a large overhead which will require resources at both the ends.