@vocovo/sparkplug-host-app

Provides reusable logic for Sparkplug Host Applications.

Intentionally designed to be:

• Not tied to a particular MQTT Client implementation
  • this makes it easier to unit test
  • and gives users of this package more flexibility to use other clients
• To not be concerned with how different Sparkplug messages are handled
  • so that different hosts can implement only the logic they need

Installation

npm install @vocovo/sparkplug-host-app

Usage

import { connectAsync } from 'mqtt'
import { UPayload } from 'sparkplug-payload/lib/sparkplugbpayload'

import { SparkplugHostApplication, EVENTS, ParsedTopic } from '@vocovo/sparkplug-host-app'

const main = async () => {
  const host = new SparkplugHostApplication('hostId')
  // Instantiate your own MQTT client
  const mqttClient = await connectAsync('mqtt://localhost:1883', {
    will: sparkplugHostApp.getOrInitializeWill(),
  })

  // Making your MQTT client compatible with the MQTTClient interface
  sparkplugHostApp.setMqttClient({
    on: mqttClient.on.bind(mqttClient),
    subscribe: mqttClient.subscribeAsync.bind(mqttClient),
    publish: mqttClient.publishAsync.bind(mqttClient),
  })

  await host.start()

  host.on(EVENTS.NBIRTH, (parsedTopic: ParsedTopic, decodedPayload: UPayload) => {
    // Will be called whenever an NBIRTH message is received
    // Handle it however you want
  })

  host.on(EVENTS.NDEATH, (parsedTopic: ParsedTopic, decodedPayload: UPayload) => {
    // Will be called whenever an NDEATH message is received
    // Handle it however you want
  })

  host.on(EVENTS.NDATA, (parsedTopic: ParsedTopic, decodedPayload: UPayload) => {
    // Will be called whenever an NDATA message is received
    // Handle it however you want
  })

  // To terminate the session correctly, we should eventually call the 'shutdown' method
  await host.shutdown()
}

main()