Node.JS Cloud IoT Core sample

config.json

{
    "projectID": "[[YOUR-PROJECT-ID]]",
    "region": "[[YOUR-REGION]]",
    "registryID": "[[YOUR-REGISTRY-ID",
    "device": "[[YOUR-DEVICE-ID"
}

gistfile1.txt

{
  "name": "cloud-iot-nodejs",
  "description": "Node.JS Sample for Cloud IoT Core",
  "author": "Your Name <your@email.com>",
  "version": "0.0.1",
  "dependencies": {
    "jsonwebtoken": "^8.2.1",
    "mqtt": "^2.17.0"
  }
}

index.js

/*globals require */
/*jshint esversion: 6 */

const mqtt = require("mqtt");
const fs = require("fs");
const jwt = require("jsonwebtoken");

// Google Cloud IoT Core specific configuration: projectID, region &c.
const c = require("./config.json");

const host = "mqtt.googleapis.com";
const port = 8883;
const clientID = `projects/${c.projectID}/locations/${c.region}/registries/${c.registryID}/devices/${c.device}`;

const roots = fs.readFileSync("./roots.pem");  // Replace with the location to your local https://pki.goog/roots.pem
const key = fs.readFileSync("./key.pem");      // Replace with the location to your private key file; generates JWT

const username = "unused";
const password = jwt.sign({
    aud: c.projectID,
    exp: Math.floor(Date.now()/1000 + 24*3600),
}, key, {
    algorithm: "RS256"
});

const topics = {
    pub: `/devices/${c.device}/events`,
    sub: `/devices/${c.device}/config`
};
    
const options = {
    host: host,
    port: port,
    clientId: clientID,
    ca: roots,
    username: username,
    password: password,
    rejectUnauthorized: false,
    protocol: "ssl",
    clean: false
};

const client = mqtt.connect(options);

client.on("connect",()=>{
    console.log("[connect}");
});
client.on("message", (topic, message)=>{
    console.log(`[message] ${topic}: ${message}`);
});

client.subscribe(topics.sub);

client.publish(topics.pub, `${new Date(Date.now()).toISOString()} Hello Henry!`);