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Comment by shurcooL | Hacker News Reader

Can I get some feedback on the following idea please:

- Maintain an open (but idle) websocket connection on your page to have an accurate real-time visitor information. The websocket should remain open as long as the user doesn't close the tab or navigate away.

What are some cons that prevent everyone from doing so?

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I have many tabs open that I'm not actually "on." I just took a shower and left HN open, for example. Can it detect that the tab is "active" or "focus?" That may help. But I'm not sure this is a problem worth a ton of work. It's, at best, a proxy for measuring things like interest.

    document.addEventListener('visibilitychange', onVisibilityChange);

Yeah, as you say, even if it just tells if a tab is open (active or inactive), that's already a good measure of interest.

But I think it may be possible to determine if the current tab is open with some javascript, and send that information through the websocket. Edit: what bsimpson said.

~50% of visitors don't have websocket support, and there is not, afaik, a free service offering such, and otherwise, it is probably not straightforward enough for the 99% to setup.

You can see a sample in action here [1]. The page should list every single person in the world (whose browser supports websockets) who is currently on that page. You can open multiple tabs and see that whenever you close/navigate away, your corresponding entry will disappear.

[1] https://dl.dropboxusercontent.com/u/8554242/live-status.html

Error: TypeError: sock is undefined

Ubuntu, Firefox 20.0

I just debugged this. The issue is that Firefox doesn't allow insecure websocket connections from https.

So either change the url to http://dl.dropboxusercontent.com/u/8554242/live-status.html or override the network.websocket.allowInsecureFromHTTPS setting in about:config to true.

Everyone does do so already (though not necessarily with websockets; occasional pings are sufficient and more widely supported). Google Analytics has a real-time dashboard. So do most web analytics platforms these days.

How do you ping a browser? Where can I find more info about this.

I figured the real-time dashboard of Google Analytics must be doing something similar, but I don't know what exactly they use.

The browser pings the server.

    setInterval(function() {
        $.ajax('http://analytics-site.com/ping?page=' + window.location.href);
    }, 5000);

Ah, makes sense, thanks.

GA realtime does not differ in tracking methodology, it uses the same onload beacon, just like the long-tail reporting.

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