FiddlerCap Already Running

6 posts, 0 answers
  1. Brandon
    Brandon avatar
    2 posts
    Member since:
    Jun 2015

    Posted 15 Jun 2015 Link to this post

    Hello. I'm trying to get FidderCap running on a laptop for one of our users, and when trying to open the program it states "FidderCap is already running on this machine". I've uninstalled and reinstalled, and have done reboots, but the program never launches. Has anyone else experienced this, and if so, is there a way around it?

     Machine is running Win7 x64. I can install it on other machines with the same build and it works just fine.

  2. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 15 Jun 2015 Link to this post

    Hello,

    The "FiddlerCap is already running on this machine" message appears when the global mutex named Global\FiddlerCap is present, indicating that at least on user on the machine is running FiddlerCap already.

    Now, you've said that you've "done reboots" which is interesting-- FiddlerCap (generally) doesn't run on its own, and restarting your machine would presumably be closing any existing instances.

    If you try to run Fiddler in that user's account, does it work?

    Regards,
    Eric Lawrence
    Telerik
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  3. Brandon
    Brandon avatar
    2 posts
    Member since:
    Jun 2015

    Posted 15 Jun 2015 in reply to Eric Lawrence Link to this post

    I've tried multiple users accounts to no avail. They all state the same thing, and it's definitely not running. It's not listed in processes or services in any way.
  4. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 15 Jun 2015 Link to this post

    Hi, Brandon--

    Are you trying to run in a guest or similarly-limited account?

    SysInternal's Process Explorer's (https://technet.microsoft.com/en-us/sysinternals/bb896653) Search feature will allow you to see who owns the Global\FiddlerCap mutex (called a mutant in that UI).

    Knowing whether you can successfully launch Fiddler (www.getfiddler.com) would be useful because it would help us understand whether the system in question has a general problem obtaining mutexes, or something similar. (And because Fiddler does everything FiddlerCore can do, it might serve as a workaround for the moment).

    Regards,
    Eric Lawrence
    Telerik
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  5. Nico
    Nico avatar
    1 posts
    Member since:
    Oct 2014

    Posted 22 Jul 2015 Link to this post

    Hi

    I am getting the same message.

    See the result of my search with Process Explorer.

     

     

  6. Eric Lawrence
    Admin
    Eric Lawrence avatar
    833 posts

    Posted 23 Jul 2015 Link to this post

    Hi, Nico & Brandon--

    Further investigation here revealed that the problem is that AVG antivirus has a problem wherein it slows down your computer so much that the check for a running instance times out, which causes the warning dialog in question. We've reached out to AVG about fixing their bug but they haven't said whether they will fix it.

    In Fiddler v4.5.1.4 we have introduced a workaround where it will just wait longer if you have buggy software interfering with the proper function of your computer.

    Regards,
    Eric Lawrence
    Telerik
    Do you want to have your say when we set our development plans? Do you want to know when a feature you care about is added or when a bug fixed? Explore the Telerik Feedback Portal and vote to affect the priority of the items
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