...The 'device' class wraps mqtt.js to provide a secure connection to the AWS IoT platform and expose the mqtt.js interfaces upward. It provides features to simplify the handling of intermittent connections, including progressive backoff retries, automatic re-subscription upon connection and queued offline publishing with a configurable drain rate. Beginning with Release v2.2.0 of the SDK, AWS collects usage metrics indicating which language and version of the SDK is being used.