Fiddler not working with .Net Core

4 posts, 0 answers
  1. Mike
    Mike avatar
    1 posts
    Member since:
    Sep 2008

    Posted 07 Jul Link to this post

    I have a console app that communicates with a number of 3rd party services via http. The original version of the app is developed for the .net Framework and Fiddler is able to successfully all of the https calls that the app makes.

    I have ported the app to .Net Core 2.1. Fiddler is not capturing the HTTPS calls made by the .Net Core version of the app.

    Any ideas as to why Fiddler is not working with the .Net Core app?

     

  2. Alexander
    Admin
    Alexander avatar
    336 posts

    Posted 10 Jul Link to this post

    Hello,

    It is possible that .NET Core is using WinHTTP instead of WinINET, for which Fiddler is configured as proxy. You can find how to set the WinHTTP proxy manually in this answer. Does this fix the problem?

    Regards,
    Alexander
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  3. Peter
    Peter avatar
    3 posts
    Member since:
    Apr 2015

    Posted 10 Jul in reply to Alexander Link to this post

    I had similar experience with console app on .Net Core 2.0 but then I switched target framework to Core 2.1 and things magically started to work.

     

    I was using this example (Client Credentials flow) to trace OpenID protocol communications: https://github.com/IdentityServer/IdentityServer4.Samples/tree/release/Quickstarts/1_ClientCredentials

  4. Alexander
    Admin
    Alexander avatar
    336 posts

    Posted 11 Jul Link to this post

    Hello Peter,

    Based on this blog post your experience makes perfect sense. It seems that from .NET Core 2.1 HttpClient does not use WinHTTP anymore and have brand new implementation (simplified explanation, for full detail check the blog post).

    Regards,
    Alexander
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