Getting error while sending notification to iOS from ASP.NET C#

int port = 2195;
           string hostname = "gateway.sandbox.push.apple.com";
         //  String hostname = "gateway.push.apple.com";
           String certificatePath = Server.MapPath("PushnotificationDev.p12");
           X509Certificate2 clientCertificate = new X509Certificate2(System.IO.File.ReadAllBytes(certificatePath), "password");
           X509Certificate2Collection certificatesCollection = new X509Certificate2Collection(clientCertificate);

           TcpClient client = new TcpClient(hostname, port);
           SslStream sslStream = new SslStream(client.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);

           try
           {
              // client.Connect(hostname,port);
               //sslStream.AuthenticateAsServer(hostname, certificatesCollection, SslProtocols.Default, true);
               ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3;
               sslStream.AuthenticateAsServer(clientCertificate, false, SslProtocols.Ssl3, true);
               MemoryStream memoryStream = new MemoryStream();
               BinaryWriter writer = new BinaryWriter(memoryStream);
               writer.Write((byte)0);
               writer.Write((byte)0);
               writer.Write((byte)32);

               writer.Write(ConvertToByteArray("9865ac6c888e9b9e819b15772e6bcb11d64c659d331a28cf7674050a20fa895p"));
               String payload = "{\"aps\":{\"alert\":\"" + "Hi,, This Is a Sample Push Notification For IPhone.." + "\",\"badge\":1,\"sound\":\"default\"}}";
               writer.Write((byte)0);
               writer.Write((byte)payload.Length);
               byte[] b1 = System.Text.Encoding.UTF8.GetBytes(payload);
               writer.Write(b1);
               writer.Flush();
               byte[] array = memoryStream.ToArray();
               sslStream.Write(array);
               sslStream.Flush();
               client.Close();
           }
           catch (System.Security.Authentication.AuthenticationException ex)
           {
               client.Close();
           }
           catch (Exception ex)
           {
               lblenc.Text = ex.Message;
               client.Close();
           }