@spalger/kibana/src/plugins/elasticsearch/lib/__tests__/findPort.js

Kibana is an open source (Apache Licensed), browser based analytics and search dashboard for Elasticsearch. Kibana is a snap to setup and start using. Kibana strives to be easy to get started with, while also being flexible and powerful, just like Elastic

var Promise = require('bluebird');
var portscanner = require('portscanner');

module.exports = function findPort(start, end, host) {
  host = host || 'localhost';
  return new Promise(function (resolve, reject) {
    portscanner.findAPortNotInUse(start, end, host, function (err, port) {
      if (err) return reject(err);
      resolve(port);
    });
  });
};