如何使用swift 3发送实时设备到设备通知？

import UserNotifications

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
    // 注册远程通知
    UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge]) { (granted, error) in
        if granted {
            DispatchQueue.main.async {
                application.registerForRemoteNotifications()
            }
        }
    }
    return true
}

func application(_ application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data) {
    let token = deviceToken.map { String(format: "%02.2hhx", $0) }.joined()
    print("Device Token: \(token)")
}

func application(_ application: UIApplication, didFailToRegisterForRemoteNotificationsWithError error: Error) {
    print("Failed to register for remote notifications: \(error.localizedDescription)")
}

import UserNotifications

func sendRealtimeNotification() {
    let content = UNMutableNotificationContent()
    content.title = "实时通知"
    content.body = "这是一条实时设备到设备通知"
    content.sound = UNNotificationSound.default()

    let request = UNNotificationRequest(identifier: "realtimeNotification", content: content, trigger: nil)

    UNUserNotificationCenter.current().add(request) { (error) in
        if let error = error {
            print("Failed to send realtime notification: \(error.localizedDescription)")
        }
    }
}