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AutoRespond while being offline

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Fiddler Classic

This is a migrated thread and some comments may be shown as answers.

9 Answers, 1 is accepted

answered on 10 Oct 2019, 02:03 PM

Hi Patrick,

At this time, Fiddler can only work with HTTP-based Protocols. The only exception to this rule is FTP where Fiddler converts the FTP download to a HTTP GET Request. Removing the SSH tunneling should work when offline.

I hope this helps. Please let me know if you need any additional information. Thank you for using the Fiddler Forums.

Regards,

Eric R | Technical Support Engineer
Progress Telerik

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answered on 11 Oct 2019, 07:43 PM

Hi Patrick,

I did some testing locally and found a few things to try and have listed them below.

1. The EXACT keyword wouldn't allow HTTPS. This only worked for HTTP.

2. Use Microsoft Edge in the newest version of Fiddler, 5.0.20194.

3. Close and reopen the browser upon changing rules.

Note that this can be tested against any website. I recommend trying the rule against another website like, www.google.com to verify that it works there. If so, this may be an issue with the Application.

Lastly, if the session publicly routed, i.e. if the request is passing through because it is bypassing the rule, then unplugging the network cable will stop Fiddler from processing the session.

Please give these items a try and let me know the results. Thank you for using Fiddler.

Regards,

Eric R | Technical Support Engineer
Progress Telerik

answered on 14 Oct 2019, 03:32 PM

Hi Eric,

thanks for your investigations!

Yes, it's indeed working when I switch from HTTPS to HTTP. Is there a technical reason for it?

From my point of view, Fiddler shouldn't feel the need to connect to the remote host on HTTPS when the following applies:

- SSL Decryption on
- Autoresponder match for the request in question

In this case I'd expect Fiddler to process the request as follow:

1. Receive request from client
2. Testing Autoresponder rules
3. Find a Autoresponder match with mapping to local file
4. No passthrough connection to the remote host because Fiddler already has everything it needs
5. Responding the file's content back to the client, using the Fiddler certificate

So I'm wondering if this limitation to HTTP when being offline is a missing feature, a bug or a technical requirement?

Thanks again
Patrick

answered on 15 Oct 2019, 08:31 PM

Hi Patrick,

After discussing with my colleagues the observed behavior is what we expect. To elaborate, in this case Fiddler is not handling the CONNECT requests properly. This is because the browser makes two HTTP requests, a CONNECT to Fiddler and a HTTP Method to the server. See the below screenshot for a visual reference.

To resolve the issue, there are two options listed below.

1. Uncheck the Unmatched requests passthrough checkbox.

2. Add the following script to the CustomRules.js file in the OnBeforeRequest method.

   // Add to OnBeforeRequest
   if (bWorkingOffline && oSession.HTTPMethodIs("CONNECT"))
   {
      oSession["X-ReplyWithTunnel"] = "Work offline; generate a fake tunnel...";
   }

For more details about the Fiddler AutoResponder, see the Using AutoResponder without Internet Forum Post.

Please let me know if you need any additional information. Thank you for using the Fiddler Forums.

Regards,

Eric R | Technical Support Engineer
Progress Telerik