mqtt.js

var awsIot = require('aws-iot-device-sdk');

var device = awsIot.device({
  keyPath: "./private.key",
  certPath: "./cert.pem",
  caPath: "./root-CA.crt",
  clientId: "name-of-thing",
  host: "https-endpoint",
});

device
  .on('connect', function() {
    console.log('connect');
    device.subscribe('topic');
  });

device
  .on('message', function(topic, payload) {
    console.log('message', topic, payload.toString());
  });

device
  .on('error', function(e) {
    console.log('error', e);
  });

device
  .on('close', function() {
    console.log('closed');
  })