IIS Express

ASP.NET Core: An attempt was made to access a socket in a way forbidden by its access permissions

This morning I made some changes to a project for a future post. Minor stuff and nothing that should have caused issues, but when I tried to run the project I got the following error from Kestrel.

warn: Microsoft.AspNetCore.Server.Kestrel[0]
Unable to bind to https://localhost:5001 on the IPv4 loopback interface: ‘An attempt was made to access a socket in a way forbidden by its access permissions.’.
warn: Microsoft.AspNetCore.Server.Kestrel[0]
Unable to bind to https://localhost:5001 on the IPv6 loopback interface: ‘An attempt was made to access a socket in a way forbidden by its access permissions.’.
crit: Microsoft.AspNetCore.Server.Kestrel[0]
Unable to start Kestrel.
System.IO.IOException: Failed to bind to address https://localhost:5001.

I had limited time so I switched the project over to launch using IIS Express and hit run, but this resulted in the following error.

HTTP Error 500.35 – ANCM Multiple In-Process Applications in same Process

Switching back to Kestrel and changing the port number in the applicationUrl setting in the launchSettings.json file fixed the issue. Later I came back to the application and tried to track down what was using the same ports and couldn’t find anything. After a reboot, all worked fine with Kestrel and the original port numbers.

For the IIS Express error, I ended up having to delete the .vs directory which can be found in the same directory as your solution file if you are using Visual Studio 2019. Thanks to stackoverflow for this fix.

Wrapping Up

Not the post I set out to write this week, but hopefully this will save someone some searching in the future, more than likely myself.

ASP.NET 5 IIS Express Configuration and OAuth 2

I am still in the process of getting all the features from my ASP.NET 4 contacts application moved into ASP.NET 5. Today I was working on getting OAuth 2 working with Google. All the code changes are in the Startup.cs in the root of the project.

In the Configuration function the options need to be set for Google authentication. This is where you set your client ID and secret. I covered the steps of getting this information from Google in this post if you need a reference.

services.Configure<GoogleAuthenticationOptions>(options =>
    options.ClientId = "Your Client ID";
    options.ClientSecret = "Your Client Secret";

In the Configure function add the following.


The above is changing the Configuration and Configure functions which are pretty similar names that could be clearer. Configuration is where services are registered withASP.NET 5’s built in dependency injection container. Examples of potential services include Entity Framework, MVC, Web API, Application Settings and in my case Google Authentication.

The Configure function is where the HTTP request pipeline is set up. This can include things like serving static files, error handlers, MVC routes and Web API routes.

At this point I tried to run and use Google to login. I was greeted with at 400 – redirect_uri_mismatch. The URL my new project was using did not match the one I used when I setup OAuth with Google. I would like to say this was not a big deal, but it took me way longer to solve than I would like to admit. The settings for which port to use when debugging is in a bit of a different place than before. It can now be found on the debug tab of the project properties.


Under Other IIS Express setting there is also a check box for Enable SSL which I had to check as well since the URL I used with Google was HTTPS. In addition to the settings in the project properties I also had to edit the applicationhost file which is used by IIS Express. You can find this file in a hidden folder in the same directory as the solution file. The path is .vs\config. To find the relevant section search for your project name or for “site name=” and that should get you to the right area. I tweaked the setting I found there to match the changes I had made in my project properties. I don’t think this is something everyone will have to do and more than likely was a result of a misstep on my part.

I ended up having to manually edit my Contacts.xproj file to get the port settings I needed. The project properties UI will let you set a port, but not edit the HTTPS URL which meant I could not get the URL I need to make Google happy without manual changes. Following is the relevant portion of my Contacts.xproj file and it is the SSLPort I had to edit.


At this point I can now start the application, but I have to manually use the HTTPS URL to get auth with Google to work since I have not found away to get Visual Studio to launch the using the HTTPS URL.

The good news is Google auth does work now!