     private let _renewSubscriptionSessionManager = AFHTTPSessionManager()
     private let _unsubscribeSessionManager = AFHTTPSessionManager()
     private let _defaultSubscriptionTimeout: Int = 300
-    private var _backupSubscriptions = [Subscription]()
     private var _eventCallBackURL: NSURL? {
         let wifiInterface = "en0"
         if let address = getIFAddresses()[wifiInterface] {

                return
            }
            
            DDLogInfo("successful subscription id: \(response.subscriptionID)  timeout: \(response.timeout)")
            
            let now = NSDate()
            let expiration = now.dateByAddingTimeInterval(NSTimeInterval(response.timeout))
            
            let subscription = Subscription(subscriptionID: response.subscriptionID, expiration: expiration, subscriber: subscriber, eventURLString: eventURL.absoluteString!, manager: self)
            
            self.add(subscription: subscription, completion: { () -> Void in
                if let completion = completion {
                    completion(result: .Success(subscription))
                }
            })
            }, failure: { (task: NSURLSessionDataTask?, error: NSError) -> Void in
                if let completion = completion {
                    completion(result: .Failure(error))
                }


internal func ==(lhs: UPnPEventSubscriptionManager.Subscription, rhs: UPnPEventSubscriptionManager.Subscription) -> Bool {
    return lhs.subscriptionID == rhs.subscriptionID
}

extension UPnPEventSubscriptionManager.Subscription: ExtendedPrintable {
    var className: String { return "Subscription" }
    override var description: String {
        var properties = PropertyPrinter()
        properties.add("subscriptionID", property: subscriptionID)
        properties.add("expiration", property: expiration)
        properties.add("eventURLString", property: eventURLString)
        return properties.description
    }
}

extension AFHTTPSessionManager {
