MQTT-SN Gateway: MQTTBroker

This module is part of mqttsngw. It is responsible for handling and maintaining connections to the MQTT broker.

Factory

const Broker = require('mqttsngw-mqttbroker');
mqttsngw.attach(Broker(opts));

Creates a new MQTTBroker factory and attaches it to an existing instance of mqttsngw. opts has the following fields:

• log: Optional. An object containing logging callbacks for all log levels (error, warn, info, debug). Every callback is called with a human-readable message as the first argument followed by an object containing more information regarding the event: { error: (msg, info) => { ... }, ...}.
• broker: Mandatory. Callback function for creation of individual client configuration based on the clientId: (clientId) => clientOpts. clientOpts is an object:
  • url: Mandatory. URL pointing to the broker.
  • All other options accepted by the connect method of MQTT.js

State Machines

[MQTTBroker] Main

• listening: Listens for incoming connection requests from the event bus. If a request is received, a new instance of [MQTTBroker] Client is created and started.

[MQTTBroker] Client

Handles connection to the broker.

• init: Preparing the state machine.
• connect: Tries to connect to the broker.
• connected: The connection has been successfully established.

Events

Several events are consumed and emitted by the MQTTBroker module on the event bus.

Consumed

| Event | State Machine | Description | | ------------------------------ | ---------------------- | ----------- | | brokerConnect,,req | [MQTTBroker] Main | Connection request | | brokerSubscribe,,req | [MQTTBroker] Client | Request subscription to a topic | | brokerUnsubscribe,,req | [MQTTBroker] Client | Request unsubscribing a topic | | brokerPublishFromClient,,req | [MQTTBroker] Client | A sensors publishes a message to the broker | | brokerPublishToClient,,res | [MQTTBroker] Client | Response whether a message has been published to a client | | brokerDisconnect,,call | [MQTTBroker] Client | Disconnect from the broker |

Emitted

| Event | State Machine | Description | | ------------------------------ | ---------------------- | ----------- | | brokerConnect,,res | [MQTTBroker] Client | Response to a connection request | | brokerSubscribe,,res | [MQTTBroker] Client | Response to a subscription request | | brokerUnsubscribe,,res | [MQTTBroker] Client | Response to a unsubscribe request | | brokerPublishFromClient,,res | [MQTTBroker] Client | Response whether a message has been published to the broker | | brokerPublishToClient,,req | [MQTTBroker] Client | The broker publishes a message to the client | | brokerDisconnect,,notify | [MQTTBroker] Client | Informs the client that the connection has been closed |