The preview mode doesn't correctly inform the user about port occupied.

[dohooo]

Describe the bug

First of all, I want to thank the author team for making such an amazing work!~

When I had a 5000 port service, vite preview did not detect the port occupation and executed the service as usual, but the service could not respond normally.

It took me a whole afternoon to find this problem. Later, I found that a function of MAC OS occupied port 5000, but Vite didn't give me the corresponding prompt, so I couldn't access Preview normally,

I am aware of this PR(#6300) and will be modifying ports 5000 to 4000, but I don't think this is a good solution to this problem. I am a newbie and I am sure there are many other newbies who have spent some time here as I have.

I try to use the "net" modules to check for port occupancy, and I find it works fine. But I can't say why. I would like to submit PR if possible.

Reproduction

https://github.com/dohooo/vite-reproduction

yarn

yarn anotherServer
yarn preview

I think it should give me a corresponding prompt when I do yarn preview.

System Info

System:
    OS: macOS 12.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 30.22 GB / 64.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 14.18.1 - ~/.nvm/versions/node/v14.18.1/bin/node
    Yarn: 1.22.17 - /opt/homebrew/bin/yarn
    npm: 6.14.15 - ~/.nvm/versions/node/v14.18.1/bin/npm
  Browsers:
    Chrome: 97.0.4692.71
    Safari: 15.2
  npmPackages:
    @vitejs/plugin-react: ^1.0.7 => 1.1.4 
    vite: ^2.7.2 => 2.8.0-beta.2

Used Package Manager

yarn

Logs

No response

Validations

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• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[dohooo]

Can I check whether there are any ports occupied on localhost / 127.0.0.1 when detecting port occupancy? @Niputi

Would love to commit a PR