Today, I bumped into something utterly strange: requests replayed through Fiddler 2 to a locally running ASP.NET Development Server on Vista using localhost URLs did not give a connection.
I use ASP.NET from both C# and Delphi Prism. Most of my development work is on Windows XP (see notes below) but I test on many platforms.
Moving one of the projects from XP to Vista, and testing with Fiddler, I found that when using Fiddler 2:
This form of URL fails on Vista, but works on XP: http://localhost:49703
This form of URL works both on Vista, and XP: http://127.0.0.1:49703
So on Vista – contrary to XP – localhost requests from Fiddler were in fact being sent to the external network adapter on Vista, and the 127.0.0.1 requests to the internal network adapter.
Since the ASP.NET Development Server is bound only to the internal network adapter, external requests don’t work (boy, I wish they did, it would make some of my debugging so much easier!).





