this.publish = function()

in device/index.js [832:852]


   this.publish = function(topic, message, options, callback) {
      //
      // If filling or still draining, push this publish operation
      // into the offline operations queue; otherwise, perform it
      // immediately.
      //
      if (offlineQueueing === true && (_filling() || drainingTimer !== null)) {
         if (_trimOfflinePublishQueueIfNecessary()) {
            offlinePublishQueue.push({
               topic: topic,
               message: message,
               options: options,
               callback: callback
            });
         }
      } else {
         if (offlineQueueing === true || !_filling()) {
            device.publish(topic, message, options, callback);
         }
      }
   };