HTTP Polling, Long Polling, HTTP streaming and WebSockets

I have read many posts on so and the web regarding the keywords in my question title and learned a lot from them. Some of the questions I read is related to specific implementation challenges while others focus on general concepts. I just want to make sure I understood all of the concepts and the reasoning why technology X is invented over technology Y and so on. So here goes:

Http Polling: Basically AJAX, using XMLHttpRequest.

Http Long Polling: AJAX But the server holds the response unless the server have an update, as soon as the server have an update, it send s it and then the client can send another request. Disadvantage is the additional header data, needs to being sent back and forth causing additional overhead.

Http Streaming: Similar to long polling but the server responds with a header with "Transfer encoding:chunked" and hence we don't need t o Initiate a new request every time the server sends some data (and hence save the additional header overhead). The drawback here is, we have to ' understand ' and figure out the ' structure of the data to distinguish between multiple Chunks sent by the server.

Java Applet, Flash, Silverlight: They provide the ability to connect to sockets servers over TCP/IP but since they is plugins, developers don ' t want to DEP End on them.

WebSockets: They is the new API which tries to address the short comings of above methods in the following Manne R:

• The only advantage of WebSockets over plugins like Java Applets, Flash or Silverlight was that WebSockets be natively Buil T into browsers and does not rely on plugins.
• The only advantage of WebSockets over HTTP streaming is so you don ' t has a effort to "understand" and a parse th E data received.
• The only advantage of WebSockets over Long Polling are that of elimination of extra headers size & opening and closing of socket connection for request.

Is there any and significant differences that I am missing? I ' m sorry if I am re-asking or combining many of the questions already on so into a single question, but I just want to Ma Ke perfect sense out of a all the info that's out there on so and the web regarding these concepts.

There is more differences than the ones you have identified.

Duplex/directional:

• Uni-directional:http poll, long poll, streaming.
• Bi-direcitonal:websockets, plugin Networking

In order of increasing latency (approximate):

• WebSockets
• Plugin Networking
• HTTP Streaming
• HTTP Long-poll
• HTTP Polling

CORS (Cross-origin support):

• Websockets:yes
• Plugin Networking:flash via policy request (not sure about others)
• HTTP * (some recent support)

Native binary data (typed arrays, blobs):

• Websockets:yes
• Plugin Networking:not with Flash (requires URL encoding across Externalinterface)
• HTTP *: Recent proposal to enable binary type support

Bandwidth in decreasing efficiency:

• Plugin Networking:flash sockets is raw except for initial policy request
• Websockets:connection Setup handshake and a few bytes per frame
• HTTP Streaming (re-use of server connection)
• HTTP long-poll:connection for every message
• HTTP poll:connection for every message + No data messages

Mobile Device Support:

• Websocket:ios 4.2 and up. Some Android via Flash emulation or using Firefox for Android or Google Chrome for Android which both provide native WEBSO Cket support.
• Plugin networking:some Android. Not on IOS
• HTTP *: Mostly Yes

Javascript usage complexity (from simplest to most complicated). Admittedly complexity measures is somewhat subjective.

• WebSockets
• HTTP poll
• Plugin Networking
• HTTP Long poll, streaming

Also Note that there are a proposal for standardizing HTTP streaming called Server-sent Events. It is currently fairly early in it's evolution and is designed to provide a standard Javascript API with comparable simpli City to WebSockets.

HTTP Polling, Long Polling, HTTP streaming and WebSockets