Re: Cookie flexibility and limitations

When you are receiving content via HTTP, you are always going to get the whole header in a particular format. To set a cookie, you are required to send it as part of this header but before the content type is passed to the browser. i.e.:

Set-Cookie: blahblahblah
Content-type: text/html

<html>
.....
[download]

Where blahblahblah is the properly formatted cookie information. When banner adverts print their info, they do something along the lines of (but possibly not exactly - hey its only an example :P)

Set-Cookie: blahblahblah
Content-type: image/gif
....
<data>
[download]

Although the cookie section is not part of the HTTP spec (according to my O'Reilly book) - everyone uses it (as we all well know :P).

So if you want to do something after the page has been displayed, you're best bet is to have a perl script that delivers a blank image with the cookie as part of its transaction to the browser. i.e:

  <img src="http://www.mysite.blob/cgi-bin/imager.pl?IMAGE=one">
[download]

As far as I know - this is the only way you can have cookies from one site set by another (by the second site including that image).

Hope that helps - if not - reply and I'll see what I can do :)

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Re: Re: Cookie flexibility and limitations by legLess (Hermit) on Jul 21, 2001 at 02:09 UTC
That's very helpful, thanks. What I missed in my thinking was that images can be served with their own HTTP header. It all makes sense now. -- man with no legs, inc.	[reply]