On Sunday 25 July 2004 2:00 pm, Todd Landfried wrote:
> How does one know if a given packet is destined for a proxy server or not?
One doesn't. That's why transparent proxying can work - proxies accept
normal HTTP requests in exactly the same format as those sent direct to
servers.
> Is there something in the packet that I can look for that tells me this?
No. You can sometimes (but not always) tell from the reply that it came
through a proxy, but you can't tell from the request.
> I know there's the port, but HTTP traffic also uses port 80.
Proxies commonly use port 8080 or 3128.
> The reason I ask is because the proxy address sometimes changes.
I don't understand (I think). Are you trying to intercept HTTP requests from
browsers (in which case you just intercept *all* TCP port 80/8080/3128
traffic, no matter where it's addressed to), or are you saying that you can't
keep track of where to redirect it to, because the proxy address moves around
(in which case you're as stuck as someone running a browser would be, trying
to direct requests to a moving proxy).
What exactly is the problem?
Regards,
Antony.
--
"I estimate there's a world market for about five computers."
- Thomas J Watson, Chairman of IBM
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