nixfilter-mqtt/utils.js

Filters for publishing and subscribing to MQTT topics, similar to "mosquitto_pub" and "mosquitto_sub"

'use strict';
var add_common_arguments, connect_to_mqtt_broker, disconnect_from_mqtt_broker, mqtt;

// Add those arguments to <argument_parser> that all filter have in common
add_common_arguments = function(argument_parser) {
  argument_parser.addArgument(['--host', '--broker', '-b'], {
    defaultValue: 'localhost',
    help: 'The hostname or IP address of the MQTT broker'
  });
  argument_parser.addArgument(['--port', '-P'], {
    type: 'int',
    defaultValue: 1883,
    help: 'The port of the MQTT broker'
  });
  argument_parser.addArgument(['--username', '-u'], {
    help: 'The username to use when connecting'
  });
  argument_parser.addArgument(['--password', '-p'], {
    help: 'The password to use when connecting'
  });
  argument_parser.addArgument(['--client_id', '-c'], {
    help: 'The client ID to use when connecting'
  });
  argument_parser.addArgument(['--qos', '-q'], {
    type: 'int',
    choices: [0, 1, 2],
    defaultValue: 0,
    help: 'The QOS level to use'
  });
  argument_parser.addArgument(['--status_topic', '-s'], {
    help: 'The (optional) MQTT topic to publish online/offline status messages to'
  });
  argument_parser.addArgument(['--online_message'], {
    defaultValue: 'online',
    help: 'The (retained) message to publish to the (optional) MQTT topic when going online'
  });
  argument_parser.addArgument(['--offline_message'], {
    defaultValue: 'offline',
    help: 'The (retained) message to publish to the (optional) MQTT topic when going offline'
  });
  return argument_parser;
};

// Require the "mqtt" module
mqtt = require('mqtt');

// Connect to the MQTT broker, using the arguments/parameters in <args>
connect_to_mqtt_broker = function(args) {
  return new Promise((resolve, reject) => {
    var connect_options, mqtt_client;
    connect_options = {
      servers: [
        {
          host: args.host,
          port: args.port
        }
      ],
      clientId: args.client_id
    };
    if (args.username) {
      connect_options.username = args.username;
      connect_options.password = args.password;
    }
    if (args.status_topic) {
      connect_options.will = {
        topic: args.status_topic,
        payload: args.offline_message,
        qos: args.qos,
        retain: true
      };
    }
    mqtt_client = mqtt.connect(connect_options);
    mqtt_client.once('connect', () => {
      if (args.status_topic) {
        mqtt_client.publish(args.status_topic, args.online_message, {
          qos: args.qos,
          retain: true
        });
      }
      resolve(mqtt_client);
    });
    mqtt_client.once('error', (error) => {
      reject(error);
    });
    mqtt_client.once('close', () => {
      reject(`Unable to connect to MQTT broker ${args.host}:${args.port}`);
    });
  });
};

// Disconnect MQTT client <mqtt_client> from the MQTT broker it is connected to
disconnect_from_mqtt_broker = function(mqtt_client) {
  return new Promise((resolve, reject) => {
    mqtt_client.end(function() {
      return resolve(mqtt_client);
    });
  });
};

// What this module exports
module.exports = {
  add_common_arguments: add_common_arguments,
  connect_to_mqtt_broker: connect_to_mqtt_broker,
  disconnect_from_mqtt_broker: disconnect_from_mqtt_broker
};

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