Hi @Markus Freitag,
If you use Visual Studio's built-in web server (IIS Express), localhost is mapped by default. If you need to access the application through 127.0.0.1, you need to configure it. The following is the test I did:
I created a default project in VS, and when I choose to run this project using IIS express, I can access it normally via https://localhost:44365.
But if I change localhost to 127.0.0.1, the same error as yours will appear.
This is because I didn't configure it in the project. Next do the following.
1.Edit applicationhost.config located inside .vs\config (".vs" dirctory is hidden) in your project and add bindings for 127.0.0.1 for http and https:
<sites> ... <site name="asp.net test" id="2"> <!-- your asp.net project --> ... <bindings> <binding protocol="https" bindingInformation="*:44365:localhost" /> <binding protocol="http" bindingInformation="*:55250:localhost" /> <binding protocol="https" bindingInformation="*:44365:127.0.0.1" /> <binding protocol="http" bindingInformation="*:55250:127.0.0.1" /> </bindings> </site> ... </sites>
2.Edit Project Url settings in VS: from solution explorer under the project tree > [your project] > properties > Web: change localhost to 127.0.0.1.
3.Save the changes and re-run the application, this time I can access the application using 127.0.0.1.
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