The way in which notifications for updates are displayed on the Stack Overflow website

Could someone shed some light on how the real-time update messages on this platform are created?

For instance, when I am composing a response to a question and a new answer is added, I receive a notification message at the top of the page. How is this functionality achieved?

I understand that HTML5 WebSockets or server-side technologies like ServerSocket could be used for this purpose. Are there any alternative methods to create similar push notification systems using Java, Spring, and jQuery?

I'm unsure about the correct tags for this question. Please advise if changes are needed.

javajavascriptajax

Answer №1

SO utilizes the innovative reverse ajax/comet technology to display messages in real-time. I recall engaging in a conversation on meta regarding this functionality, though locating the exact link eludes me currently. I will provide an update once I locate it.

Depending on the programming language and framework used, the terminology may vary (e.g., websockets or socket.io), but ultimately they all stem from the comet framework.

Update:

For further insights, here is the discussion on SO meta pertaining to this topic.

Answer №2

My experience with the Direct Web Remoting framework has been extremely positive. (DWR).

Answer №3

There are multiple methods to accomplish this:

  • Polling: By utilizing JQuery, you can regularly send a request (e.g., every 5 seconds) to retrieve updates from the server.
  • Streaming: When you send a request, the server does not specify a Content-Length in the response and keeps the socket open indefinitely. This allows for data to be sent from the server to the client at any time. However, it also means that a connection is maintained by your server for each client.
  • Long polling: A combination of the previous two methods. The server maintains the connection but with a timeout. If no new data is available, the server closes the connection and the client reopens a new one after a period of time.

These are known as Push technologies: http://en.wikipedia.org/wiki/Push_technology

Naturally, there are other approaches to achieve the same goal.

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