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From Filip Hanik - Dev Lists <devli...@hanik.com>
Subject Re: What is a typical Comet event flow, with multiple READ events?
Date Wed, 03 Jun 2009 12:41:59 GMT
When a browser is a client, you typically don't have multiple read events.

Filip

Pieter Fibbe wrote:
> Hi,
>
> I have been trying to write a Comet webapp, but it's not totally clear
> to me when and how CometEvents are exactly triggered. According to the
> documentation a "typical life cycle of a Comet request will consist in
> a series of events such as: BEGIN -> READ -> READ -> READ ->
> ERROR/TIMEOUT" (from: http://www.mbaworld.com/docs/aio.html).
>
> It seems that a READ event is triggered only by a POST request, but
> the "event flow" that I am getting never triggers more that one READ
> event in a row, for example: BEGIN-> ->READ->END, BEGIN-> ->READ->END,
> etc. Is the way a comet application should work? So you have to
> establish a new connection every time you get a response from the
> server and wait for the next response, process it and start from the
> beginning? My idea was having one connection and reuse that connection
> for multiple requests. So on the client side there would be something
> like the following code:
>
>
> <script>
> var xhr;
> function init() {
> 	xhr = new XMLHttpRequest();
> });
>
> function triggerEvent() {
> 	xhr.open("POST", "/servlets/cometservlet", true);
> 	xhr.send("something");
> }
> </script>
> <input type="button" onclick="triggerEvent" />
>
>
> Since it is not possible to invoke xhr.send() several times without
> opening the connection first (xhr.open()), a CometEvent.BEGIN is
> always triggered first. So how can the "BEGIN -> READ -> READ -> READ"
> series (given in the documentation) be implemented?
>
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>   


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