Re: Lack of support for "If-Modified-Since"

John W. James (jjames@firstfloor.COM)
Thu, 13 Feb 1997 17:02:24 -0800


Turns out that several of the servers (I know Netscape does this) require
that you feed back in the identical date that's on the document on the
other side for you to get back a 304. In other words, if (ifModifiedSince
== file.mtime()) return 304 else return 200

John

At 03:25 PM 2/13/97 -0500, you wrote:
>
>I'm finding that a lot of servers don't support 'If-Modified-Since'
>conditional GET's, even ones such as Netscape.com and Microsoft.com. The
>application that I'm writing will be re-checking selected URLs every few
>weeks for updates, so in the interest of preserving bandwidth, I'd like this
>to work.
>
>Using LWP (for perl), I use the following line to ask remote servers for any
>documents that are less then half a day old:
>$request->header('If-Modified-Since' => HTTP::Date::time2str(time-40000));
>
>
>Many responses come back '304', but about one third of them are *still*
>'200'. NCSA, Netscape and Apache servers all seem to be guilty and
>not-guilty of this, depending on whose site you visit.
>
>Is there something I'm doing wrong?
>
>
>Dan Howard
>Industry Canada
>(613) 596-0201
>
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>

---------------------------------------------------------------
John James Email: jjames@firstfloor.COM
First Floor, Inc. Web: http://www.firstfloor.COM
444 Castro Street, Suite 200 Tel: (415) 254-5101
Mountain View. CA 94041 Fax: (415) 968-1193

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