ajax - how does Google gmail, docs, etc. get its push-notification of changes? -


i assume there ajax request on client side polls updates, amazingly tight response. can provide more insight tricks may doing in protocol?

two methods used in case

  • polling: javascript code polls server every (for instance) 10 seconds see if there fresh news show

  • persistent connection: xmlhttprequest request performed client, , server keeps connection until there news (replies data client in case), or if given time-out reached - client tries again , on.

google uses 2nd option, replying , updating faster.


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