`svelte-kit dev` does not recognize occupied ports on Windows

Describe the bug When running svelte-kit dev, on Windows, SvelteKit does not throw an error for an already occupied port. Instead what happens is SvelteKit prints the “welcome” message, when trying to reach the started dev server it is of course shadowed by the process already occupying that port.

To Reproduce

On a Windows machine:

1. Make sure some service is running on port 3000.
2. Make a new directory and cd into it.
3. npm init svelte@next
4. npm i
5. npm run dev ⬅ This should throw, but doesn’t!

Expected behavior

An error should be thrown to indicate that the port the dev server is trying to launch on is already in use by another process.

Information about your SvelteKit Installation:

Diagnostics

• The output of npx envinfo --system --npmPackages svelte,@sveltejs/kit,vite --binaries --browsers

  System:
    OS: Windows 10 10.0.19042
    CPU: (4) x64 Intel(R) Core(TM) i5-4460  CPU @ 3.20GHz 
    Memory: 16.23 GB / 23.92 GB
  Binaries:
    Node: 14.15.4 - C:\Program Files\nodejs\node.EXE      
    Yarn: 1.22.10 - ~\AppData\Roaming\npm\yarn.CMD        
    npm: 6.14.10 - C:\Program Files\nodejs\npm.CMD        
  Browsers:
    Chrome: 89.0.4389.114
    Edge: Spartan (44.19041.423.0), Chromium (89.0.774.75)
    Internet Explorer: 11.0.19041.1
  npmPackages:
    @sveltejs/kit: next => 1.0.0-next.71
    svelte: ^3.29.0 => 3.37.0
    vite: ^2.1.0 => 2.1.5

Severity

Mildly annoying, but for many users nonetheless.

Additional context I poked around in the source for the svelte-kit cli. I noticed that you guys use the port-authority package’s blame function. According to the port-authority documentation, under Additional functions, this function only supports Unix-like operating systems.

Maybe a better fix is for this, would be to add support for this in port-authority, just thought this should be tracked.

Thanks for this awesome framework!

[benmccann]

Ok, it sounds like there isn’t anything you want to be fixed still then, so I’ll go ahead and close this

[bluwy]

@Cheetah0723 Please ask around discord for support questions. GitHub issues is not the place for it.