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Slack App only works when Fiddler tool is open

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Fiddler Classic
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Jacob
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Jacob asked on 21 Jul 2020, 05:39 PM

Hi team,

 

I recently downloaded Fiddler Classic and now that is downloaded, my Slack app does not connect unless the Fiddler tool is up and running. What settings do I need to change in order to have Fiddler closed and ability to use the Slack app?

 

Thanks,

Jacob

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Nick Iliev
Telerik team
answered on 22 Jul 2020, 10:25 AM

Hello Jacob,

 

From the provided details, it looks like that when Fiddler is turned off, the OS proxy settings are probably not reset (to use no proxy or the default system proxy). If no proxy is set, your Windows settings should look like the ones in the fiddler-no-proxy.png image(when no Fiddler is running). When Fiddler is running, the proxy settings should have set 127.0.0.1:8888 (default proxy for Fiddler), as shown in the second image (fiddler-proxy-classic.png).

Try resolving the issue by making sure that Capture is turned off,  then closing Fiddler, closing the Slack client, and restarting the Slack client. If the problem persists, then open the Proxy Settings OS window and make sure that your settings are reverted (the Fiddler proxy should not be present when Fiddler is turned off).

Apart from the above, it is known that some network tools might interrupt the Slack client, as stated in the official Slack documentation. Check this page for additional information and instructions.

 

Regards,
Nick Iliev
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Charles
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commented on 06 Apr 2022, 10:21 PM

Thanks Nick for the heads up, but are you going to fix this issue? I spent most of the day, trying to work out why both Slack & MS Teams App on Windows 10, would no longer work.
It was only when I opened Fiddler Classic, that I realised what was going on. 
Fiddler really should reset the system proxy back to what it was, before Fiddler was installed, each time it is Quit. I would say this is definitely a bug. 
Nick Iliev
Telerik team
commented on 07 Apr 2022, 06:00 AM

Hey Charles,

 

Fiddler Classic is resetting the system proxy by default, except when on some corner cases where the application was terminated unexpectedly (and then there is not much Fiddler could do as the application has already been shut down).

As a side note, our new Fiddler Everywhere has an improved proxy configuration mechanism that "remembers" and recovers the OS proxy settings, even if the previous app instance was closed unexpectedly,

Charles
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commented on 07 Apr 2022, 07:43 AM

Hi Nick

Thanks for the response. If it is not always possible to reset the system proxy, would it be possible to at least show a big alert, telling the user that the system proxy could not be reset.

This would be very helpful, because I had no idea that Fiddler was changing the system proxy? I spent a day wondering why many of my internet connections had failed.

This was incredibly frustrating and worrying. 

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Jacob
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Nick Iliev
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