Mini Chat : Subscription for refresh

I am trying to design a mini-chat for my website

I am almost ready to go but I'm not sure about my refresh method.

My first thought is to use something like :

// Call the refresh method every 30sec.
setInterval(refresh,30*1000);

But I remember some articles about managing some kind of subscription in a web app.

Someting like this :

   CLIENT                           SERVER
      |                               |
onConnection ----- Subsribe ------->  |
      |                               |
      |  <---------- Notify ------ onUpdate
      |                               |
   onQuit ------ Unsubscribe ------>  |

Do you have any help / tutorials ?

I found this ressource, but I'm not sure I can use the SIP protocol in my website : RFC 6665 - Section 3 - SIP Methods for Event Notification

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Other ressources I found :

• SIPML5 : HTML5 SIP client


• OpenSIPS : an Open Source SIP proxy/server