fiddler
When I open fiddler, http traffic from browser can be captured.
I wrote a program using .net HttpWebRequest, the traffic can also be captured.
Also using python urllib2, fiddler captures the http traffic.
Does fiddler capture all http traffic from my machine when I open fiddler without changing any default setting of fiddler? There's no custom filter of fiddler.
Fiddler is supposed to be proxy server. what does it do when it's opened?
See this screenshot. Located at the top right part of the screen
I hope I do not misinterpret the problem -- I assume localhost traffic to be the thing that cannot be captured.
localhost traffic is routed via the local loopback interface (a 'virtual' interface that routes local traffic more efficiently), and this never reaches a network card. Most packet capture tools capture the packets on the network device driver layer and thus only capture packets that actually go throug physical network devices.
Best Answer
Fiddler is a proxy server. It captures HTTP, HTTPS, and FTP traffic that is sent to it, and then forwards that traffic to the server.
By default, when Fiddler starts, it sets itself as the "system" proxy. Most, but not all applications will automatically send their traffic to Fiddler for that reason. Virtually all other applications can be reconfigured to proxy their traffic through Fiddler.