code: function isLegalPort (port) {
    if ((typeof port !== 'number' && typeof port !== 'string') ||
        (typeof port === 'string' && port.trim().length === 0)) {
      return false
    }
    return +port === (+port >>> 0) && port <= 0xFFFF
  }
docs: Check that the port number is not NaN when coerced to a number, is an integer and that it falls within the legal range of port numbers.