I'm curious as to how fiddler is able to capture traffic when you use the URL ipv4.fiddler. Is ipv4 a special domain that resolves local and fiddler just registers with http.sys to proxy the call?
Any insight would be great.
+4
A:
Easy: Fiddler is a proxy, it gets to see almost(*) all of the requests. When it sees a request bound for "ipv4.fiddler", it simply changes it to 127.0.0.1.
(*)The only reason Fiddler needs this at all is that some HTTP stacks are hardcoded to bypass the proxy for "localhost" addresses. By using the magic string "ipv4.fiddler", you can circumvent that hardcoded restriction.
A:
when fiddler is running go into ie (if running ie) and check your proxy settings, youll see fiddler has set itself up as a proxy between you and the internet. Its worth knowing this when fiddler crashes, most commonly in my situation is when "fiddling" streaming and forgetting to tell fiddler that it is handling a stream, if fiddler crashes and you cant access the internet, its because running fiddler has set a proxy in internet explorer and because it crashed it didnt get chance to revert the setting
Matt
2010-05-21 22:53:47