IOS CLLocation in the background

I have been working on an app to send the GPS position of the cell phone to a server through a TCP socket. The application must be able to remain in the background indefinitely. I have part of the echo code, the application sends the packet over TCP and the server receives it, it remains in the background but after a certain time the application stops sending data to the server. Apparently IOS closes it. If someone has any ideas or has done something similar, I would greatly appreciate your comments. This is the code I have:

class Location:NSObject, CLLocationManagerDelegate {

private var locationManager = CLLocationManager()
private var errorLocation: Bool = false
private var stuffLocation: CLLocation!

var outSocket: OutSocket!
var timer: NSTimer!
var stuff: Stuff!

override init() {
    super.init()
    outSocket = OutSocket()
    setupLocation()
}

func setupLocation() {
    locationManager.delegate = self
    locationManager.desiredAccuracy = kCLLocationAccuracyBest
    locationManager.requestWhenInUseAuthorization()
    locationManager.activityType = CLActivityType.Fitness
    locationManager.allowsBackgroundLocationUpdates = true
    locationManager.startUpdatingLocation()
}

func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
    if !errorLocation {
        errorLocation = true
        locationManager.allowDeferredLocationUpdatesUntilTraveled(10, timeout: 50)
        stuffLocation = locations[0]
        if timer == nil {
            timer = NSTimer.scheduledTimerWithTimeInterval(5, target: self, selector: #selector(Location.sendDataToServer), userInfo: nil, repeats: true)
        }
    }
}
}
func locationManager(manager: CLLocationManager, didFinishDeferredUpdatesWithError error: NSError?) {
    errorLocation = false
}

The sendDataTiServer function is responsible for sending the data via TCP to the server. Any comment is welcomed. Greetings.