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POHTML5: using manifest fallback to check user's connectivity
 

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  1. POHTML5: using manifest fallback to check user's connectivity
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    <p>I'm focusing on offline web applications with HTML5 at the moment. I came to the point where I need a reliable method of checking the user's connection to determine whether he/she is online or offline at the moment. Since I learned that the navigator.onLine property is highly unreliable I found a very nice method using the Fallback area of the cache manifest. I implemented two similar solutions from two different books, one being "Introducing HTML5" (Lawson/Sharp) and one "HTML5: The Missing Manual" (MacDonald). I guess this is an issue of HTTP caching (I use Apache and localhost), which I don't really know too much about. I pasted my code, it's a few files, but very little code.</p> <p>The adapted solution from Introducing HTML5: <a href="http://pastebin.com/UGsmnAtK" rel="nofollow">http://pastebin.com/UGsmnAtK</a></p> <p>The adapted solution from HTML5 - the missing manual: <a href="http://pastebin.com/8v5ck3E6" rel="nofollow">http://pastebin.com/8v5ck3E6</a></p> <p>Tested with Chrome 16...</p> <p>=== What I want ===</p> <ul> <li>start app with empty cache and running apache</li> <li>click the button -> alert "Online" is shown</li> <li>stop apache</li> <li>click the button -> alert "Offline" is shown</li> <li>start apache</li> <li>click the button -> alert "Online" is shown</li> </ul> <p>=== What happens ===</p> <p>Introducing HTML5 solution: - start app with empty cache and running apache - click the button -> alert "Online" is shown - stop apache - click the button -> alert "Online" is shown - start apache - click the button -> alert "Online" is shown</p> <p>HTML5: the missing manual solution: - start app with empty cache and running apache - click the button -> alert "Online" is shown - stop apache - click the button -> alert "Online" is shown - start apache - click the button -> alert "Online" is shown</p> <p>Other scenarios and use cases fail in similar fashion. The books promise that you can check the user's connectivity any time using their methods. So I guess I'm doing something wrong here. I would thankfully embrace any ideas on this topic.</p> <p>Cheers, Felix</p>
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