Proper way to detect user's leaving page

I am building a WebApp (ERP) and I need to display the people currently logged in and active on the page. I managed to get something pretty accurate by listening on the mouse/keyboard events and periodically reporting to the DB.

I don't know how to mark people offline when they close the page. I tried using onbeforeunload, but it obviously fires when the user simply changes pages (click a link inside the ERP, that point to another page in the ERP).

I then tried to use WebSockets, but the problem is the same : everytime the page is realoded, the WebSockets connection is closed.

So I can think of two ways:

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  Use WebSockets indeed, and replace all links by a call to a javascript function that would somehow tell the server that the user is going to change page (so that the server doesn't mark it as offline). But that doesn't feel right, semantically speaking, links should be links, it simply points to another location.

  
  


• 
  

  Use either WebSockets or AJAX and never actually change page: links are replaces by a function that will call for the content, and display it on screen (updating the DOM with Javascript). But again, it doesn't feel right either, because semantically speaking the page would have no meaning and the URL would never change, so the user can't "copy paste" the link of the page to refer to it, right ?

  
  

So, is there a proper, clean way of doing this? Thanks for your help.