With the advent of HTML 5, is there a point in using COMET anymore?

I am very tempted to use long wait http or periodic polling by the client to set up pseudo-sockets on the browser side, for an application that would be used publicly.

But then on the 2nd thought, I am thinking HTML 5 is here.

But on the 3rd thought, what is the percentage of browsers out there that remain non-HTML5 within 12 months, 24 months, 36 months? If there are at least 20% of browsers still incapable of HTML5, then I cannot depend on HTML5 because 20% of users not being able to access an application is a significant amount.

What do you think, how would your advice be (to me and to developers in general)?

Q1. Is there any point in rigging in COMET 开发者_如何学编程into an application anymore? I am thinking of gwt comet - http://code.google.com/p/gwt-comet/.

Q2. Should we release a new public application within the next 2 months that is dependent on HTML5 sockets and tell non-HTML5 browser users "sorry, your browser version cannot access this application"?

Or should we architect the apps to use communication like GWT RPC?

Q3. I am also very distrustful of long wait http request. I have never used it before but I have a horrible feeling about it. I have been using 10 to 20 second client-side polling. Is long wait http request risky (risk of hanging a browser session)? Does long wait request present any additional security risk?

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If you're interested in being a good citizen, yes, you should absolutely tell people that you don't support their browser in 2 months. The only reason IE6 keeps hanging around is because developers keep bending over backwards to support it, while all they're doing is allowing users to continue to function with a horribly broken and insecure browser. IE8 is reasonably good, and IE9 is great (time to release unclear though), and all the modern Webkit/Opera/Gecko-based browsers are "good enough", and tend to have user bases that upgrade more frequently than IE.

Of course, market penetration is always a big problem, and a consideration when you're trying to make money from a product. I recognize that telling people that their browser sucks isn't always an option, but more people need to consider it - we need to get rid of these legacy browsers, and that won't happen until we stop supporting them.

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Well, if you take into account the time it took/its taking to get rid of IE6, I would not rely much on HTML5 for an app that you want the masses to use.

:)

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HTML5 is a client side technology - Comet is a server side one. The real question is when will Servlet 3.0 be implemented? that will replace Comet.