/// In your AppDelegate or UIViewController
import MQTT
mqtt = MQTT(clientID: clientID, host: "mqtt.example.com", port: 1883, username: username, password: password)
mqtt.delegate = self
mqtt.cleanSession = false
mqtt.start()

/// You MUST stop MQTT service when app did enter background, otherwise NWConnection will fail and NSTimer won't stop!
func applicationDidEnterBackground(_ application: UIApplication) {
mqtt.stop()
}

/// MQTT will start a new connection between client and broker.
func applicationWillEnterForeground(_ application: UIApplication) {
mqtt.start()
}