Why setting env variables for ports such as ASPNETCORE_HTTP_PORT doesn't work in Visual Studio

Question

I have such a startup profile for my project in launcSettings.json.

"http": {
  "commandName": "Project",
  "launchBrowser": true,
  "launchUrl": "swagger",
  "environmentVariables": {
    "ASPNETCORE_ENVIRONMENT": "Development",
    "ASPNETCORE_HTTP_PORTS": "8087",
    "ASPNETCORE_HTTPS_PORTS": "8088"
  }

But the application opens on port 5000. Why is this happening? When starting in docker-compose and specifying these environment variables, the application opens on the correct ports.

Answer 1

It seems that Visual Studio forcibly sets ASPNETCORE_URLS when starting the application - see this question:

"ASPNETCORE_URLS": "https://localhost:5001;http://localhost:5000"

when applicationUrl and ASPNETCORE_URLS are not specified in the start profile (which is your case).

This interferes with setting the ports separately:

"ASPNETCORE_HTTP_PORTS": "8087",
"ASPNETCORE_HTTPS_PORTS": "8088"

When I run from Visual Studio 2022 under .NET 8 with your configuration I get:

warn: Microsoft.AspNetCore.Hosting.Diagnostics[15]
      Overriding HTTP_PORTS '8087' and HTTPS_PORTS '8088'. Binding to values defined by URLS instead 'https://localhost:5001/;http://localhost:5000/'.
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: https://localhost:5001
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://localhost:5000

This doesn't happen when you use the same profile (e.g. named Dev) from the command line (or supply the env variables via Docker as your initial test)

dotnet run --launch-profile Dev

Output:

info: Microsoft.Hosting.Lifetime[14]
      Now listening on: http://[::]:8087
info: Microsoft.Hosting.Lifetime[14]
      Now listening on: https://[::]:8088
info: Microsoft.Hosting.Lifetime[0]
      Application started. Press Ctrl+C to shut down.

So the issue is Visual Studio. I am not sure how to turn off this behavior with a program setting, but the workaround I found answering the other question is to set ASPNETCORE_URLS to empty in launchSettings.json:

"environmentVariables": {
  "ASPNETCORE_ENVIRONMENT": "Development",
  "ASPNETCORE_URLS": "",
  "ASPNETCORE_HTTP_PORTS": "8087",
  "ASPNETCORE_HTTPS_PORTS": "8088"
}

I've tested this and it works for your case too on Visual Studio 2022 17.12 (.NET 8/ASP.NET 8)