Unable to connect to web server "IIS Express" ... its baaaackkk

Coreysan 1,736

I've done everything stackoverflow mentioned:

Deleted the .vs folder
Initalized a new AppSettings.json file
Changed the port number
Rebooted

Nothing works. I'm still getting the error.

It doesn't make sense that I should delete the bin and/or obj folders. I have several projects, and they all have the same error.

What's the real issue here? Anyone know?

I have VS 2019, build 16.4.3, with .Net 4.8

Sidney Bezerra 0 Reputation points

2023-02-13T12:07:43.1466667+00:00

Thanks @Coreysan
That's was the solution.
Great Man !
Tks.
Marshall Penn 0 Reputation points

2023-07-05T07:52:31.9866667+00:00

Try looking at this article as it explains the problem technically : https://www.softwaremeadows.com/posts/solutions_to_error_unable_to_connect_to_web_server_iis_express/

2 answers

Bruce Zhang-MSFT 3,751 Reputation points

2022-04-08T01:45:16.257+00:00
Hi @Coreysan ,

What kind of application and what .NET version you use? Something I think you can try and if anything wrong or abnormal, I need your feedback.

Try to create an empty asp.net or asp.net core application and run it in IIS Express directly. Please tell me the result.

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.

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Bruce Zhang
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2 people found this answer helpful.
Coreysan 1,736 Reputation points

2022-04-08T03:10:03.317+00:00

I've tried deleting .vs lots of times, and it didn't solve anything.

However, changing the port number did. So that's my solution. I wonder why that's needed sometimes?

IF you want to provide this as your answer, I'll flag it answered for you!

Thanks so much!!!!

Coreysan 1,736 Reputation points

2022-04-08T03:12:09.48+00:00

BTW -

my project is a MVC Core 3.1 project with N-Tier architecture, and I use UnitOfWork.

When I created the project I chose the Core 3.1 library. I have no idea if I should rebuild
using the .Net 5 library, or upgrade VS 2019, or even move up to 2022.

A big change like 2022 kinda scares me.

Bruce Zhang-MSFT 3,751 Reputation points

2022-04-08T05:33:30.283+00:00

Hi @Coreysan ,

From what I've tried, this problem all happens randomly. But I think it's likely that IIS express is still listening on the original port because it didn't exit normally. This means that the initial port is still occupied by the process. When deleting the applicationhost.config file of IIS express and changing the port, IIS express uses another port which is not occupied by other processes and everything works.

Coreysan 1,736 Reputation points

2022-04-08T18:26:33.463+00:00

@Bruce Zhang-MSFT

That was a very satisfying answer - thanks!!! You should consider being a therapist, cuz you helped me calm down!

Corey

Bruce Zhang-MSFT 3,751 Reputation points

2022-04-11T01:16:00.253+00:00

Hi @Coreysan ,

Thank you for such a high rating. It's so nice of you can accept the answer. I am honored to be able to help you.

loverboy sfiso wilson 0 Reputation points

2023-10-19T04:06:22.8866667+00:00

Running VS as Admin resolved this issue for me
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loverboy sfiso wilson 0 Reputation points

2023-10-19T04:07:01.9833333+00:00

Running VS as Admin resolved this issue for me
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Unable to connect to web server "IIS Express" ... its baaaackkk

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