Using createServer.listen() doesn't correctly detect used ports

[zen0wu]

🐛 Bug Report

getIsPortTaken function doesn't seem to work correctly under macOS.

To Reproduce

Steps to reproduce the behavior:

1. nc -l localhost 3000 to start a minimal server locally
2. Start jest-dev-server on the same port with usedPortAction set to "ask"
3. It doesn't ask

Expected behavior

It should ask

Link to repl or repo (highly encouraged)

Please provide a minimal repository on GitHub.

Issues without a reproduction link are likely to stall.

Run npx envinfo --system --binaries --npmPackages expect-puppeteer,jest-dev-server,jest-environment-puppeteer,jest-puppeteer,spawnd --markdown --clipboard

Paste the results here:

*** Clipboard option removed - use clipboardy or clipboard-cli directly ***


## System:
 - OS: macOS 10.14.6
 - CPU: (8) x64 Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz
 - Memory: 1.98 GB / 16.00 GB
 - Shell: 5.7.1 - /usr/local/bin/zsh
## Binaries:
 - Node: 12.10.0 - /usr/local/bin/node
 - Yarn: 1.17.3 - /usr/local/bin/yarn
 - npm: 6.11.3 - /usr/local/bin/npm
 - Watchman: 4.9.0 - /usr/local/bin/watchman
## npmPackages:
 - jest-dev-server: ^4.3.0 => 4.3.0

[domoritz]

I'm running into this issue. This bug breaks Jest in VSCode since the local server keeps running and different runs fail all the time.

[BitFis]

~Same issue here, this still seems to be broken~

Should be working, be sure that the port config is set to the correct port:

jest-puppeteer.config.js

module.exports = {
  server: {
    command: `npm start`,
    port: 3000, // if set correctly should work
    usedPortAction: 'ask'
  },
  exitOnPageError: false
}

The getIsPortTaken function checks the provided port by trying to start a server on that specific port. Test configured port by adding: console.log('conigured port:', config.port); at node_modules\jest-dev-server\lib\global.js:173 (using jest-puppeteer v4.4.0)

[gregberge]

Fixed in #518