You can't do a chat application just using JSP... JSP just gets translated down to HTML, and the user has to use HTTP for communication. Basically that means the user has to make a request before the server can generate a response. This communication style isn't condusive to a chat application. To do a chat application you're going to need to embed an applet or some other component (ActiveX, etc.) in the page created by your JSP that can use a communication mechanism other than the request/response style of HTTP to perform the real-time communication needed for a chat application. There are lots of ways to do this, and I'm sure you can find many existing examples of chat applets just by searching google. If you want more information about developing your own chat applet, you could also ask about that specific topic in another forum that it better fits in - Applets, Distributed Java, or Sockets - depending on what you need help with.
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