code: function (requestedPortCount) {
      var self      = this,
          promises  = [],
          totalPorts = this._getMaxServers() * (requestedPortCount + 1);
  
      for (var i = 0; i < totalPorts; i++) {
        promises.push((function () {
          return self._getOpenPort();
        })());
      }
  
      return Promise.all(promises);
    }
docs: Functional._getOpenPorts() -> Array
  Allocates a port for each server instance, and each requested port per each server instance