code: function findUnixPortRange() {
    var cmd;
    if (process.platform === 'sunos') {
      cmd =
          '/usr/sbin/ndd /dev/tcp tcp_smallest_anon_port tcp_largest_anon_port';
    } else if (fs.existsSync('/proc/sys/net/ipv4/ip_local_port_range')) {
      // Linux
      cmd = 'cat /proc/sys/net/ipv4/ip_local_port_range';
    } else {
      cmd = 'sysctl net.inet.ip.portrange.first net.inet.ip.portrange.last' +
          ' | sed -e "s/.*:\\s*//"';
    }
  
    return execute(cmd).then(function(stdout) {
      if (!stdout || !stdout.length) return DEFAULT_IANA_RANGE;
      var range = stdout.trim().split(/\s+/).map(Number);
      if (range.some(isNaN)) return DEFAULT_IANA_RANGE;
      return {min: range[0], max: range[1]};
    });
  }
docs: Computes the ephemeral port range for a Unix-like system.
  @return {!webdriver.promise.Promise.<{min: number, max: number}>} A promise
  that will resolve with the ephemeral port range on the current system.