How do I test proxy authentication?

I am trying to authenticate a proxy in a vb.net app.

HOW DO I TEST TO SEE IF THE PROXY IS AVAILABLE? I have tried this website but it is not working for me. How do I get the "Login" to work? I am trying to use this. Dim fiddler As New Fiddler.FiddlerWebRequest() IOParam = "user@mydomain.com" Password = "secretpassword". Fiddler.Url = "" fiddler.Credentials = New System.NetworkCredential(IOParam, Password)
Fiddler.Proxy = New Fiddler.FiddlerWebProxy("mail.com", 9090)
You need to set the FiddlerTransport property of the Fiddler instance to TCP (and not HTTPS). This is where the credentials get passed in.FiddlerWebRequest()

IOParam = "user@mydomain.NetworkCredential(IOParam, Password) fiddler.FiddlerWebProxy("mail.com", 9090)
Fiddler.Transport = Fiddler.Tcp

How do I test my proxy connection on Windows?

I am trying to use a HTTPS proxy connection to a web API server on Windows and am not sure how to test the connection without going through the full packet capture process. I have tried manually entering the IP address and port in the proxy settings, but the connection fails with an error stating "A proxy was not found."
Is there a way to test the proxy connection without having to manually setup packet capture? You may also run the command ipconfig /all C:MyIP.txt.

Then you can simply read the last line of the file and test it with the following http command (eg if the IP address is 10.10, run http 10.10).

The proxy will be working if the IP address and the port in the URL are matching with the output IP address and port from the command.