mqttsngw-core

MQTT-SN Gateway: Core

This module is part of mqttsngw. It is responsible for handling parsed MQTT-SN packets from the event bus and maintaining state machines for connected sensors. If necessary it requests a connection to the broker on the event bus.

Factory

const Core = require('mqttsngw-core');
mqttsngw.attach(Core(opts));

Creates a new Core 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) => { ... }, ...}.
• enforceUniqueClientIds: If set to true, existing connections will be disconnected if a new connection with the same MQTT Client ID is established.

State Machines

[Core] Main

• init: Preparing the state machine
• listening: Listens for incoming connection requests from the sensor network. If a request is received, a new instance of [Core] Client is created and started.

[Core] Client

Reflects the current sensor state.

• init: Preparing the state machine.
• willTopic: Waits for a will topic sent by the sensor.
• willMessage: Waits for a will message sent by the sensor.
• connectBroker: Tries to connect to the broker.
• active: The sensor is connected. Depending on the received sensor messages, it will start the state machines [Core] Subscribe, [Core] PublishToBroker or [Core] PublishToClient.
• sleep: The sensor may enter sleep state by stating a non-zero duration in the DISCONNECT packet. The gateway will collect ingress publishes from the broker and sends them to the sensores once it's active again.

[Core] Subscribe

Handles topic subscription requested sent by sensors.

• init: Checks subscription request.
• brokerSubscribe: Subscribes the topic at the broker.

[Core] PublishToBroker

Sends a message to the broker

• init: Checks the publish request and translates the topicId to the topic name.
• publishToBroker: Sends the message to the broker.

[Core] PublishToClient

Sends a message to the sensor

• init: Lookup the topicId to the given topic name or register one.
• registerTopic: Registers a topic at the sensor.
• publishToClient: Sends the message to the sensor.

Events

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

Consumed

Event	State Machine	Description
snUnicastIngress,*,connect	[Core] Main	Incoming connection requests packet
brokerConnect,*,res	[Core] Client	Response to a broker connection request
snUnicastIngress,*,disconnect	[Core] Client	Sensor sent disconnect
snUnicastIngress,*,register	[Core] Client	Sensor registers a new topic name
snUnicastIngress,*,subscribe	[Core] Client	Sensor subscribes to a new topic
snUnicastIngress,*,unsubscribe	[Core] Client	Sensor unsubscribes from a topic
snUnicastIngress,*,publish	[Core] Client	Sensor publishes a message
snUnicastIngress,*,pingreq	[Core] Client	Sensor sent ping request
brokerDisconnect,*,notify	[Core] Client	Connection to the broker has been disconnected
brokerPublishToClient,*,req	[Core] Client	A message shall be sent from the broker to the sensor
brokerSubscribe,*,res	[Core] Subscribe	Response to a subscription request
brokerUnsubscribe,*,res	[Core] Unsubscribe	Response to a desubscription request
brokerPublishFromClient,*,res	[Core] PublishToBroker	Response to a publish to broker request
snUnicastIngress,*,regack	[Core] PublishToClient	Reaction to a register request from the sensor
snUnicastIngress,*,puback	[Core] PublishToClient	Reaction to a publish request from the sensor

Emitted

Event	State Machine	Description
brokerConnect,*,req	[Core] Client	Request a connection to the broker
brokerDisconnect,*,call	[Core] Client	Disconnect from the broker
snUnicastOutgress,*,connack	[Core] Client	Send a CONNACK to the sensor
snUnicastOutgress,*,disconnect	[Core] Client	Disconnect from sensor
snUnicastOutgress,*,regack	[Core] Client	Send a REGACK to the sensor
snUnicastOutgress,*,pingresp	[Core] Client	Respond to a ping request
brokerSubscribe,*,req	[Core] Subscribe	Subscribes a topic at the broker
snUnicastOutgress,*,suback	[Core] Subscribe	Respond to a subscription request
brokerUnsubscribe,*,req	[Core] Unsubscribe	Unsubscribes a topic at the broker
snUnicastOutgress,*,unsuback	[Core] Unsubscribe	Respond to a desubscription request
brokerPublishFromClient,*,req	[Core] PublishToBroker	Publish a message to the broker
snUnicastOutgress,*,puback	[Core] PublishToBroker	Send PUBACK to the sensor
snUnicastOutgress,*,register	[Core] PublishToClient	Register a topic at the sensor
snUnicastOutgress,*,publish	[Core] PublishToClient	Publish a message to the sensor
brokerPublishToClient,*,res	[Core] PublishToClient	Respond to publish request from the broker