In what situations would AJAX long/short polling be preferred over HTML5 WebSockets?

Question

I am building a small chat application for friends, but unsure about how to get information in a timely manner that is not as manual or as rudimentary as forcing a page refr

Answer 1

• XHR polling A Request is answered when the event occurs (could be straight away, or after a delay). Subsequent requests will need to made to receive further events.

  The browser makes an asynchronous request of the server, which may wait for data to be available before responding. The response can contain encoded data (typically XML or JSON) or Javascript to be executed by the client. At the end of the processing of the response, the browser creates and sends another XHR, to await the next event. Thus the browser always keeps a request outstanding with the server, to be answered as each event occurs. Wikipedia

• Server Sent Events Client sends request to server. Server sends new data to webpage at any time.

  Traditionally, a web page has to send a request to the server to receive new data; that is, the page requests data from the server. With server-sent events, it's possible for a server to send new data to a web page at any time, by pushing messages to the web page. These incoming messages can be treated as Events + data inside the web page. Mozilla

• WebSockets After the initial handshake (via HTTP protocol). Communication is done bidirectionally using the WebSocket protocol.

  The handshake starts with an HTTP request/response, allowing servers to handle HTTP connections as well as WebSocket connections on the same port. Once the connection is established, communication switches to a bidirectional binary protocol which does not conform to the HTTP protocol. Wikipedia