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Re: Reload page... without disconnect ?

From: Frederic Artru <artru@apple.com>
Date: Wed, 11 Dec 96 12:45:42 -0800
Message-Id: <199612112046.MAA19218@scv1.apple.com>
To: Royans K Tharakan <rkt@poboxes.com>, http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
>	I was searching through www.metacrawler.com
>
>	and was surprised that it reloaded a page without javascript
>	and that to with different data.
>
>	When one preses the search button.. we get a CGI response of the
>	present status of the search... and when all is done it loads 
>	a new html file... without any java script.
>
>	Infact... I had to struggle to see whether it had javascript 
>	because the cache always showed me the latest page not the
>	pre-reload page.
>
>	I tried to telnet to port 80 and see what its doing... but it
>	shuts me out before I send the http request.
>
>	Any ideas of how its being done.... BTW OS/2's webexplorer refused
>	to show me that intermediatory page... I use NETSCAPE other wise to
>	watch that effect.
>
>	I am building a http search server and want help to use this if
>	http protocol supports this process.

What you are experimenting is probably (definitely) server push. It is a 
feature of Netscape Navigator that is not part of HTTP 1.x. What it does 
is send a multipart content-type telling the client to replace each part 
with the next one (thus the page changes). Basically, this forces the 
connection to stay open (though it has nothing to do with persistant 
connection in HTTP 1.1). Servers usually push images (to create some sort 
of animation), but some also push html text (for the same purpose that 
you experimented).

Unfortunately, all servers (including some of Netscape's !) do not 
implement this consistently and the specs 
(http://partner.netscape.com/assist/net_sites/pushpull.html) are somewhat 
unclear. Server push has the drawback of forcing the client to keep the 
connection open by pretending that more data is to come. It also requires 
that the client nkows how to deal with this feature...

Explorer and Navigator both implement server push...

Hope this helps.


---------------------------------------------------------------
Frederic Artru          artru@apple.com          (408) 974-5410
Senior Engineer                                 1 Infinite Loop
Internet Platform                           Cupertino, CA 95014
---------------------------------------------------------------
Received on Wednesday, 11 December 1996 12:53:21 EST

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