Reverse Ajax

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Reverse Ajax refers to an Ajax design pattern that uses long-lived HTTP connections to enable low-latency communication between a web server and a browser. Basically it is a way of sending data from client to server and a mechanism for pushing server data back to the browser.[1][2]

This server–client communication takes one of two forms:

  • Client polling: the client repeatedly queries (polls) the server and waits for an answer.
  • Server pushing: a connection between a server and client is kept open and the server sends data when available.

Reverse Ajax describes the implementation of either of these models, or a combination of both. The design pattern is also known as Ajax Push, Full Duplex Ajax and Streaming Ajax.

Examples

The following is a simple example. Imagine we have 2 clients and 1 server, and client1 wants to send the message "hello" to every other client.

With traditional Ajax (polling):

  • client1 sends the message "hello"
  • server receives the message "hello"
  • client2 polls the server
  • client2 receives the message "hello"
  • client1 polls the server
  • client1 receives the message "hello"

With reverse Ajax (pushing):

  • client1 sends the message "hello"
  • server receives the message "hello"
  • server sends the message "hello" to all clients

Less traffic is generated with Reverse Ajax and messages are transferred with less delay (low-latency).

References

  1. Crane, Dave; McCarthy, Phil (July 2008) (in English). Comet and Reverse Ajax: The Next Generation Ajax 2.0. Apress. ISBN 1590599985. 
  2. Martin, Katherine (2007-03-22). "Developing Applications using Reverse Ajax". java.net, O'Reilly and CollabNet. http://today.java.net/pub/a/today/2007/03/22/developing-applications-using-reverse-ajax.html. 

External links

mk:Reverse Ajax
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