Last Updated: 16 Oct 2019 13:36 by ADMIN
Created on: 09 Oct 2019 15:51
Type: Bug Report
Can't connect to domains with 3 hyphens

Fiddler can't connect to domains with 3 consecutive hyphens.

This error occurs:

fiddler.network.https> HTTPS handshake to r1---sn-ab5szn7e.googlevideo.com (for #793) failed. System.ArgumentException Decoded string is not a valid IDN name.
Parameter name: unicode


To reproduce:

Start Fiddler Everywhere (at least on Mac), make sure HTTPS decryption is enabled.

Go to www.youtube.com and try to watch a video.

The aforementioned error will occur in Fiddler.

1 comment
Eric R | Senior Technical Support Engineer
Posted on: 16 Oct 2019 13:36

Hi Carsten,

This is a known issue with the System.Net.Http.HttpClient in .NET. The reason for the error is the GetAscii decoding is interpreting the --- as an IDN Name which requires a specific format as described in the RFC 3490, Section 4.1 spec. If the Uri doesn't match the format it throws the error. Microsoft has introduced a fix that can be found at the Make Idn.GetAscii Compatible with Windows GitHub Issue.

Lastly, I have increased the priority of this by adding your vote and encourage you to follow the item to receive updates.

Please let me know if you need any additional information. Thank you for providing feedback to Fiddler.


Eric R | Technical Support Engineer
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