Developing Web API in C# with VS 2022: IIS Express Error, no connection to local IP, access denied

Georg Aubele Lehmbau 0

I'm developing a Web API with C#, Net 8, in Visual Studio 2022.

Everything was fine until I changed one detail in

"$schema": "http://json.schemastore.org/launchsettings.json",
"iisSettings": {
  "windowsAuthentication": false,
  "anonymousAuthentication": true,
  "iisExpress": {
    "applicationUrl": "http://localhost:20040",
    "sslPort": 44363
  }

I changed localhost to an local IP, let's say 192.168.188.3, in order to test access from my laptop. Starting the debug mode, I got an message window with an error message:

(I'm translating from German, so the actual text could differ from the english message)

'No connection could be established to webserver IIS Express. [...] Failed to register URL "http://192.168.188.3:20040/" for site "MyAPI application /". Error description: access denied (0x80070005)'

I changed the line to its former value, but the error message comes up again and again as soon as I start the debug process. The IP does not exist in the whole source code anymore!

I already tried to delete '%USERPROFILE%\AppData\Local\Temp\IISExpress' and I also read the question https://learn.microsoft.com/en-us/answers/questions/1191901/unable-to-launch-iis-express-web-server but the solutions mentioned there do not seem to work with an API project.

Lan Huang-MSFT 29,751 Reputation points Microsoft Vendor

2024-03-08T02:23:25.55+00:00

Hi @Georg Aubele Lehmbau,

What kind of application and what .NET version you use?

solution 1 (I dont have a web pane in my properties)

Are you using ASP.NET Core? If so, maybe you can try the following steps.

Delete .vs\config\applicationhost.config file, then right click on prject solution -> properties -> debug tab ->web server settings, change port number to be different from all other applications. Restart VS and rebuild solution.
Georg Aubele Lehmbau 0 Reputation points

2024-03-08T07:33:21.2333333+00:00
Sorry, I edited the first post and added, that I develop with Net 8.
As already mentioned, I'm developing a Web API.

The location of the applicationhost.config is for me .vs/My_Project/config.
I removed it, started up VS 2024 and in project solution -> properties -> debug tab I don't see web server settings.

And even with the deleted applicationhost.config the error message appears.
The server is running - as already before deleting the config - and shows the localhost addresses that it manages.
My goals are

Get rid of that error message

Get the server running and serving content from the local IP address.
Georg Aubele Lehmbau 0 Reputation points

2024-03-08T07:41:46.58+00:00
Additional information:
Right-clicking the icon of the IIS Express server in the task menu of Windows 11, I see the ports he is listening on. And every time I change a port in the appsettings.json it ADDS another port instead of replacing it!
Example:
IIS Express shows the addresses

localhost:20040 localhost:44363

after changing the 20040 into 20041 and starting the debug session again, I see the addresses

localhost:20040 localhost:20041 localhost:44363

The 20041 should REPLACE the 20040 - at least IMHO.

The error message makes sense if the IIS ADDs every change instead of replacing the according lines. Where does the config of the IIS reside?
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1 answer

Sam Wu-MSFT 7,531 Reputation points Microsoft Vendor

2024-03-12T09:53:43.69+00:00

@Georg Aubele Lehmbau

You can try to open properties page of your web application and make it use some available port that is not in port exclusion range.

After changing port click also on Create Virtual Directory button.

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Georg Aubele Lehmbau 0 Reputation points

2024-03-13T12:08:47.4833333+00:00

As already written in the first post:

I already tried to delete '%USERPROFILE%\AppData\Local\Temp\IISExpress' and I also read the question https://learn.microsoft.com/en-us/answers/questions/1191901/unable-to-launch-iis-express-web-server but the solutions mentioned there do not seem to work with an API project.

There seems to be no tab in the settings to change a port with an API project.
And as mentioned in my second comment to the first answer, I think the problem is the IIS Express ADDING new ports instead of UPDATING them, when I change the ports in the launchSettings.json .

Has anyone a solution or a link to a solution to the IIS Express adding over and over again new adresses and ports, when changing them in this file? I cannot find the according config.

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Sam Wu-MSFT 7,531 Reputation points Microsoft Vendor

2024-03-14T09:54:51.0766667+00:00

@Georg Aubele Lehmbau

It is difficult to reproduce your problem based on your description, I suggest you open a case via: https://support.microsoft.com, one of our engineers will help find the root cause.
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Developing Web API in C# with VS 2022: IIS Express Error, no connection to local IP, access denied

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