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Comment by wallunit | Hacker News Reader

Chat rooms 10 years ago weren't using web standards like HTML, GIF and Javascript. They were writing either in Java or in Flash.

However MSIE6 also supports XmlHttpRequest (though an Active-X Control), which you can also use for real-time communication. Just setup a XmlHttpRequest and let the request idle on the server-side until new data become available.

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Wouldn't that lock up a thread, per request? Things would quickly grind to a halt I'm sure

Depends on your web server. AFAIK, nginx uses a combination of events and threads to handle a ginormous number of simultaneous connections.

See:

    http://en.wikipedia.org/wiki/Asynchronous_I/O

    http://www.slideshare.net/joshzhu/nginx-internals
    
    http://www.aosabook.org/en/nginx.html
    
    http://serverfault.com/questions/86674/why-is-nginx-so-fast

Also, Node.js.

Edit: formatting.

Only if your server code process each request in a separate thread. But that's also true, when using web-sockets or when using the GIF approach. When implementing real-time applications, you always have to write non-blocking asynchronous server code, for example using node.js or Twisted.

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