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From "Albretch Mueller" <>
Subject two questions: HTTP 1.1 headers + constantly open connections in TC
Date Fri, 08 Aug 2008 14:32:12 GMT
 1) Can you achieve such a thing as a registered, dedicated, always
open connection to each client in a network from login to logout using
tomcat?, and
 1.1)  How can browsers be configured to take advantage of them?
 1.2)  What would you suggest if I would like this configuration to be
available to different browsers, the user may have?
 This would be beneficial if you want to use an internal, local
network cache for a number of users you know in a network you own
 Which each user's login a connection is open transparently to that
user in a tomcat server that just works as a cache. Different users
are not supposed to trample on each others' connections

 2) In the (2004) article "Concerning Etags and Datestamps"
 by Lars R. Clausen, he states:
  "Avoiding download of the entire body can be done in three different ways: By
using a HEAD request first, and then GET if the content is predicted changed, by
using a GET and breaking connection after receiving the header if the content is
predicted unchanged, or by using the If-None-Match and If-Modified-Since headers
in the request. The first method involves an extra connection for each download,
which takes time and server resources. The second method requires low-level
interaction with the web client, which may be complex to implement. The third
method is preferable, though it is subject to errors if the web server does not
implement the required functionality correctly, and it may not be able
to support more
complex prediction schemes."
 The part I wouldn't totally agree with or that is not clear to me is
"The first method involves an extra connection for each download,
which takes time and server resources."
 I think when you hit a server with a "HEAD" request, the server just
returns the meta-data without trying to setup sessions or "keep-alive"
connections from that client in an unencumbered way, but if you "GET"
connections to server resources, servers will do the setup to estabish
ongoing connections to that client, so then when you drop the
connection after reading the headers, servers do keep the connection
open wondering that went of with the client . . .
 So, I think it you know that the server most likely didn't change
some data and that the particular server reliably reports HTTP
headers, then it is better to conditionally go with "HEAD" first
 Is it true? Am I missing something?

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