System.Net.Security.NegotiateStream.BeginAuthenticateAsClient C# (CSharp) Method

        public virtual IAsyncResult BeginAuthenticateAsClient(
            NetworkCredential credential,
            string targetName,
            ProtectionLevel requiredProtectionLevel,
            TokenImpersonationLevel allowedImpersonationLevel,
            AsyncCallback asyncCallback,
            object asyncState)
        {
            return BeginAuthenticateAsClient(credential, null, targetName,
                                             requiredProtectionLevel, allowedImpersonationLevel,
                                             asyncCallback, asyncState);
        }

        private void AuthCallback(IAsyncResult ar)
        {
            try
            {
                NegotiateStream nsCb = (NegotiateStream)ar.AsyncState;
                nsCb.EndAuthenticateAsClient(ar);
                nsCb.BeginRead(buffer, 0, buffer.Length, ReceiveCallback, nsCb);
                authenticated = true;
            }
            catch (Exception e)
            {
                authenticated = false;
                Console.WriteLine(e.Message);

                Console.WriteLine("Введите логин:");
                login = Console.ReadLine();
                while (login.Length == 0)
                {
                    Console.WriteLine("Введите логин:");
                    login = Console.ReadLine();
                }
                Console.WriteLine("Введите пароль:");
                password = Console.ReadLine();
                nws = new NetworkStream(socket);
                ns = new NegotiateStream(nws, true);
                netCred = new NetworkCredential(login, password);
                ns.BeginAuthenticateAsClient(netCred, String.Empty, ProtectionLevel.EncryptAndSign, TokenImpersonationLevel.Delegation, AuthCallback, ns);
            }
        }