Why can't Fiddler see my web service traffic?

web-services fiddler network-traffic
Chris picture Chris · Sep 20, 2013 · Viewed 23.8k times · Source

I had a problem that Fiddler wasn't showing my web service calls made from my application (running locally). I found and solved my problem.

So my question is not how, but why does Fiddler not show web service traffic? I have a very limited understanding of how network traffic works so this might be quite simple/obvious. All I'm able to decipher is:

  1. I don't think it has anything to do with HTTPS, as I can see HTTPS requests in Fiddler (decoded if I want through Fiddler's settings).

  2. I copied a piece of code new WebProxy("127.0.0.1", 8888); in order to get it to work so it must have something to do with proxies?

This is an ASP.NET application in case that makes a difference.

Answer

Jaqen H'ghar picture Jaqen H'ghar · Oct 20, 2016

Really old question but:

While the answer and comments hint towards the right solution, they are far from answering the question.

Fiddler sees traffic by your user account. Since web services run by the application pool identity, fiddler cannot see their traffic.

The easiest solution (and the only one that worked for me) is to change the website application pool user to run under your account

Simply:

  1. Open IIS
  2. Find your website application pool name (right click website -> Manage Website -> Advanced Settings -> Listed under Application Pool)
  3. Go to application pool advanced settings (Application Pools -> Right click your desired application pool -> Advanced Settings)
  4. Change User Account to your account (Identity -> ... -> Custom Account -> Set)

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