code: function localhost(local, defaultPort) {
    // edge case when hostname:port is not informed via cli
    if (local === undefined || local === 'true') {
      local = [defaultPort];
    } else {
      local = local.toString().split(':');
    }
  
    return {
      hostname: reIp.test(local[0]) || isNaN(parseInt(local[0], 10)) &&
        local[0] ? local[0] : os.hostname(),
      port: parseInt(local[1] || (!reIp.test(local[0]) && local[0]), 10) ||
        defaultPort
    };
  }
docs: Normalize localhost and port