Category Archives: Uncategorized

Failed to connect to a Windows service

Recently I was testing real-world performance of TP-LINK Archer T9E AC1900 wireless adapter. The experiment was quite unsuccessful and I didn’t experience any reasonable improvement. Quite the opposite: speeds did not improve but the connection was mush less stable.

After uninstalling TP-Link driver/utility package I’ve noticed that it left my Windows 10 installation quite messed up:


Really TP-Link? I was not able to use my old USB Wireless Adapter and the list of wireless networks simply wouldn’t show up. Quick Internet search helped solve the problem, resetting Winsock Catalog fixed it:

netsh winsock reset

In addition, I suspected that Windows system files might be corrupted so I decided to check:

C:\WINDOWS\system32\sfc /scannow

Beginning system scan. This process will take some time.

Beginning verification phase of system scan.
Verification 100% complete.

Windows Resource Protection found corrupt files and successfully repaired
them. Details are included in the CBS.Log windir\Logs\CBS\CBS.log. For
example C:\Windows\Logs\CBS\CBS.log. Note that logging is currently not
supported in offline servicing scenarios.

All fixed, back to more productive activities.


CS50 Lecture by Steve Ballmer

Steve Ballmer gives a great lecture at Harvard:

Update: I actually met him in ProClub locker room in Bellevue right before Christmas. It was a little surprising to see him there but I’ve heard from friends that you see him there often. So I just commented that his lecture was really good especially the aspects about luck and being hardcore. He was flattered and simply hi-fived me 🙂

Unable to open TWAIN source

This post is a deviation from my general blog theme, but I simply had to post it.

Issue: my Canon LiDE 25 scanner was working for several years on Windows 7 x64 English Pro but suddenly started to show error “Unable to open TWAIN source Please check connection Then re-start Toolbox”


Solution: add C:\Windows\twain_32\CNQL25 to PATH environment variable.  Problem solved!

Security Testing: Fuzzing

While doing Threat Model for a service I’m currently implementing, I came across an attack surface that could benefit from extensive Fuzzing. It immediately reminded me about the presentation I gave few years ago at Seattle CodeCamp which I’d like to share:

Hopefully, it was helpful. Let me know what you think!

Enabling SSL on a server endpoint in Windows

The task of enabling SSL on your server is very simple. It doesn’t require any code changes assuming your server is already listening on httpand port 443.


  • On the server install a server-side certificate (includes private key) that can be verified by the client, i.e. it chains to a Trusted Root certificate that is installed on the client. This certificate should go into Certificates (Local Computer)\Personal\Certificates\. Also, make sure that the certificate’s subject is issued for your URL.

The actual steps of configuring SSL on the server is very simple:

  1. From elevated command line execute following command to delete all previous bindings for port 443 (obviously, port can be different):
    netsh http delete sslcert ipport=
  2. From elevated command line establish binding between certificate and port:
    netsh http add sslcert ipport= certhash=YourCertHash appid={YOUR-APP-ID} certstorename=MY

Successful response to the first command is “SSL Certificate successfully deleted”, for the second is “SSL Certificate successfully added”. You can also see your SSL bindings using following command:

netsh http show sslcert

At this point you should be good to go – make a call from the client to your server and SSL should be established.

Good luck and let me know if you run into issues!