Online ajax updating

[Acute]

Hi there,
in twitter and facebook when some of your friends/follows makes new post, your page gets updated via ajax.

any ideas how it is implemented? i need the best concept/idea, not the code :]

thnx in advance

[Acute]

Hey people, help me

[McLaren]

don't know how it is done but I can try to guess.

You should make some timer in your page, which periodically checks a facebook for new posts. If there is new ones, then update your page :)

Edit: don't know how to check for those new posts in facebook, but I heard that there is some API so I guess you need to be familiar with it.

[Acute]

First thing came my mind also was periodically checking the server for new posts with ajax, but in my opinion it loads the server and database.
My suggestion is that when someone posts, server looks for online friends and performs "send_new_post" function. On the client side there is a javascript function "on_post_arrival" that will paste new arrived post. The question is how? :)
Is it actually possible to do it without periodically sending requests?

P.S.: when I wrote "in twitter and facebook" I meant them as examples)

[McLaren]

Oh, so you want get messages not from facebook or twitter, but from you own site similar to facebook :)

I just googled and found this:

http://stackoverflow.com/questions/493720/persistent-connection-using-javascript

Take a look at it and tell how succesfull you were with this :)

[McLaren]

Oh, so you want get messages not from facebook or twitter, but from you own site similar to facebook :)

I just googled and found this:

http://stackoverflow.com/questions/493720/persistent-connection-using-javascript

Take a look at it and tell how succesfull you were with this :)

[McLaren]

Why is it called Comet:

In March 2006, software engineer Alex Russell coined the term Comet in a post on his personal blog.[17] The new term was a play on Ajax (Ajax and Comet both being household cleaners, common in the USA).

:D

this is from wikipedia http://en.wikipedia.org/wiki/Comet_(programming)

For me also when I didn't know about ajax it also made me associations with cleaner :D

[Acute]

Thxn!))) Shit, I was implementing the same thing)) well, almost the same thing))) But, in my implementation the main disadvantage is that I have to create "userID".php file for each registered user, since single php file can't process many many files simultaneously.(can it?)

[McLaren]

But, in my implementation the main disadvantage is that I have to create "userID".php file for each registered user, since single php file can't process many many files simultaneously.(can it?)

I think it should be possible. Creating php files for every user looks not that good - what if you have 100K users? :)

I found here is decent tutorial:

http://www.zeitoun.net/articles/comet_and_php/start

<?php
 
  while(1) {
    echo '<script type="text/javascript">';
    echo 'comet.printServerTime('.time().');';
    echo '</script>';
    flush(); // used to send the echoed data to the client
    sleep(1); // a little break to unload the server CPU
  }
 
  ?>

So I think server should somehow check what users are logged in at every cycle, and send to them data.