How do I prevent my localhost port from changing while debugging when launching in IIS Express with-CodePudding

I have a visual studio solution for an ASP.NET Core application. This ASP.NET Core application also uses Microsoft.AspNetCore.SpaServices to render a React SPA. On some PCs, it runs as expected: when launching it in debug mode through visual studio, it loads up on the configured address and port (localhost:3000).

I recently upgraded to Windows 11. Ever since after that, when I try to run the project, visual studio will fire up a web browser, load the app on the configured port (localhost:3000), then switch to a random port! (in the 50000 range). Note that the same project, on the same version in git, launches as expected (loads and stays on localhost:3000) on other PCs running Windows 10.

Additionally, I can run other applications, like a react frontend on port 3000 at a separate time with no incident.

launchsettings.json looks like this:

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:3000",
      "sslPort": 0
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
        "environmentVariables": {
            "ASPNETCORE_ENVIRONMENT": "Development",
        }
    }
}

I saw a similar question

When I turn on tracing, I can see that Microsoft.AspNetCore.SpaServices reports a new, random port number as the port to serve the application from:

2022-12-23 10:19:32.1515|INFO|Microsoft.AspNetCore.SpaServices|You can now view myapp.name in the browser.
2022-12-23 10:19:32.1515|INFO|Microsoft.AspNetCore.SpaServices|  Local:            http://localhost:52371
2022-12-23 10:19:32.1515|INFO|Microsoft.AspNetCore.SpaServices|  On Your Network:  http://10.11.12.13:52371

(names and IP addresses anonymized.)

Why visual studio / IIS express changing this port number on load, and how can I make it stop?

CodePudding user response：

The solution for me ended up being related to zscalar's proxy behind the corporate firewall. I needed to ensure that localhost and 127.0.0.1 were added to the NO_PROXY environment variable.

The string "_sm_au_" being appended to the URL (like localhost:56912/?_sm_au_=123vAB12AB842t12" ) was a sign that zscalar was involved, as I found originally here: https://stackoverflow.com/a/72735926/18097