Async function to check if port is available in node.js

isPortAvailable.ts

/**
 * This is a modern rewrite of this gist https://gist.github.com/timoxley/1689041 using promises
 */

import { createServer } from 'net'

export async function isPortAvailable(port: number): Promise<boolean> {
  return await new Promise((resolve, reject) => {
    const testServer = createServer()

    testServer.once('error', (err) => {
      if (err.code === 'EADDRINUSE') {
        // Port is not free
        return resolve(false)
      } else {
        // Some other error happened
        reject(err)
      }
    })

    // If it starts then the port is free
    testServer.once('listening', () => {
      testServer.once('close', () => resolve(true))
      testServer.close()
    })

    testServer.listen(port)
  })
}