问连接VPN服务器时“Domain=NEVPNErrorDomain Code=1 \”(Null)\“错误

EN

func initVPNTunnelProviderManager(){

    self.vpnManager.loadFromPreferences { (error) -> Void in

        if((error) != nil) {
            print("VPN Preferences error: 1")
        }
        else {

            let p = NEVPNProtocolIKEv2()
            p.username = "******"
            p.remoteIdentifier = "*****"
            p.serverAddress = "******"

            let keychain = KeychainSwift()
            let data = keychain.getData("vpnPassword")

            p.passwordReference = data
            p.authenticationMethod = NEVPNIKEAuthenticationMethod.none
            p.useExtendedAuthentication = true
            p.disconnectOnSleep = false

            self.vpnManager.protocolConfiguration = p
            self.vpnManager.isEnabled = true

            self.vpnManager.saveToPreferences(completionHandler: { (error) -> Void in
                if((error) != nil) {
                    print("VPN Preferences error: 2")
                }
                else {

                    var startError: NSError?

                    do {
                        try self.vpnManager.connection.startVPNTunnel()
                    }
                    catch let error as NSError {
                        startError = error
                        print(startError)
                    }
                    catch {
                        print("Fatal Error")
                        fatalError()
                    }
                    if((startError) != nil) {

                        **// Here it comes first time later onwards it goes to else block. (Which I'm expecting first time too)
                        print("VPN Preferences error: 3")**

                        let alertController = UIAlertController(title: "Oops..", message:
                            "Something went wrong while connecting to the VPN. Please try again.", preferredStyle: UIAlertControllerStyle.alert)
                        alertController.addAction(UIAlertAction(title: "Dismiss", style: UIAlertActionStyle.default,handler: nil))

                        self.present(alertController, animated: true, completion: nil)
                        print(startError)
                    }
                    else {
                        print("Start VPN")
                    }
                }
            })
        }
    }
}

if((startError) != nil) { 
 // Here is control coming for first time
}
else {
// Which should always come here //later onwards its coming here, not first time.
}