Cannot debug in Visual Studio after changing the port number?

Question

I added the line .UseUrls("http://*:5000") to enable clients from other hosts accessing the web api.

    public static void Main(string[] args)
    {
        var host = new WebHostBuilder()
            .UseKestrel()
            .UseContentRoot(Directory.GetCurrentDirectory())
            .UseIISIntegration()
            .UseStartup<Startup>()
            .UseUrls("http://*:5000") // Added
            .Build();

        host.Run();
    }

However, using browser to access localhost:5000/api/Test got the error of HTTP/1.1 400 Bad Request? Should the .UseUrls() be only compiled for production?

HTTP/1.1 400 Bad Request
Date: Mon, 08 Aug 2016 21:42:30 GMT
Content-Length: 0
Server: Kestrel

The following messages are copied from Visual studio Output window when testing.

Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request starting HTTP/1.1 GET http://localhost:5000/api/Test

Microsoft.AspNetCore.Server.IISIntegration.IISMiddleware:Error: 'MS-ASPNETCORE-TOKEN' does not match the expected pairing token '9bca37f2-7eda-4517-9f8f-60b6cc05cf01', request rejected.

Microsoft.AspNetCore.Hosting.Internal.WebHost:Information: Request finished in 8.5976ms 400

Answer 1

You should call first .UseUrls() and/or .UseConfig() and then .UseIISIntegration().

When running ok under IIS/IISExpress, you end up with 2 processes. IIS listening on the desired port and Kestrel on another one. Your requests should go to IIS and then it is forwarded to Kestrel (with the MS-ASPNETCORE-TOKEN).

The call to .UseIISIntegration() hides this mapping. It actually changes the port in your app and sets IIS on the desired port. But it breaks if you call both methods in incorrect order.

You are getting this error message because Kestrel expected to run behind IIS, and received a direct request. And it noticed that because IIS was not there to inject the MS-ASPNETCORE-TOKEN header.

This issue documents the issue and may solve it in future releases.