Tukukkk

If I attempt to launch my .net core app I get this message. I realize there are many posts out there claiming to fix this but I have tried every method they suggest and none are working.

If I go into the project properties under debug and change the port, then it will connect 1 time. Then if I attempt to connect again, it will give me the same error again. I can then switch the port back to the original and it will load one time, then it will fail any time beyond that, until I switch it again. Anyone have any ideas or fixes they used?

Thanks!

I installed core 2.0 and updated VS 2017 to 15.4.3 today, had the same error.

I ended up changing the application to run on a different port, it worked for me.

I have tried to delete the vs folder but did not work.

Hope it helps.

I had this problem. There is a hidden folder in directory of project that name is '.vs'. Close the Visual Studio and delete this folder. The problem will solve.

In a solution if you have multiple projects using ASP.NET Core in Visual Studio 2017 and you are trying to use the same port number you will get this error. You must have unique port assignment in your solution.

Go here in your project: Properties/launchSettings.json open this file and edit the port numbers here. Note: This is where you change the SSL port (two places).

Reason: VS/IIS Express maintains bindings to all the ASP.NET Core projects in your solution that use IIS Express as the server. For example if you use Kestrel or some other server you will not have this problem. VS creates a new port for each app when it is created in the solution to ensure you do not have port conflicts.

If you are trying to use Azure AD registered applications reply ports and trying to "reuse" your app registration, you might think to simply change the "app's" port so that you don't have to register it in Azure; this will not work. If you are just testing apps and want to reuse a registration then you must make sure that the app you are currently working on is the ONLY one on the port - manually. If you need to test two or more apps then you must register them in Azure AD individually as you would in production.

I know there is already an accepted answer to this question, but none of the solutions worked for me and my solution may help someone. I am using VS2017 with an ASP.NET Core 2.0 Razor Pages project.

The error just started appearing for no obvious reason, and I tried the solutions posted here.

I ran the web app from the command line using the dotnet run command to see if that would bring up any meaningful errors, and there was a warning about the URL not being correctly bound. I looked in my projects PropertieslaunchSettings.json file and noticed that the applicationUrl properties were different.

1. Change the values for applicationURL so they are the same


2. Close the project and close VS


3. Delete the hidden .vs folder (as mentioned in the accepted answer)


4. Start up VS as Admin

Your app should work fine.

• If you're hard-coding a specific IP address (not localhost), check that it hasn't changed.

It could also just be that there are iisexpress.exe processes hanging around in task manager which were running on the same port.

I've just found a couple and killing them solved this problem for me without needing to delete any .vs folder or changing ports or anything like that.

I have solved this issue by
adding exclusion to file devenv.exe in windows defender (anti virus, Win10)

how to know this is the issue;
when you load project defender will notify in notification unauthorized changes blocked. if this is the issue just add the exception as above mentioned.

Tried all. didn't work above.
changing host in applicationhost.config fixed.

change localhost to 127.0.0.1

<binding protocol="http" bindingInformation="*:50740:127.0.0.1" />

<binding protocol="https" bindingInformation="*:44381:127.0.0.1" />