public static void Subscribe_OPC_UA()
        {
            UAEndpointDescriptor endpointDescriptor =
                "opc.tcp://10.92.XXX.XXX:4861";
            
            var client = new EasyUAClient();
            client.DataChangeNotification += client_DataChangeNotification_Main1;

            Console.WriteLine("Subscribing...");
            client.SubscribeMultipleMonitoredItems(new[]
                {
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB98_HEIZUNG_ISTWERTE_DR_EING_SEK_WT1_HEIZ", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB98_HEIZUNG_ISTWERTE_TEMP_AUSG_SEK_WT1_HEIZ", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB98_HEIZUNG_ISTWERTE_TEMP_EING_SEK_WT1_HEIZ", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB99_KÜHLUNG_ISTWERTE_DR_EING_SEK_WT1_KUEHL", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB99_KÜHLUNG_ISTWERTE_TEMP_AUSG_SEK_WT1_KUEHL", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB99_KÜHLUNG_ISTWERTE_TEMP_EING_SEK_WT1_KUEHL", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB98_HEIZUNG_ISTWERTE_DR_EING_SEK_WT2_HEIZ", 1000),
                    new EasyUAMonitoredItemArguments(null, endpointDescriptor,
                        "ns=3;s=DB98_HEIZUNG_ISTWERTE_TEMP_AUSG_SEK_WT2_HEIZ", 1000)
                });

            Console.WriteLine("Processing monitored item changed events for 10 seconds...");
            System.Threading.Thread.Sleep(10 * 1000);

            Console.WriteLine("Unsubscribing...");
            client.UnsubscribeAllMonitoredItems();

            Console.WriteLine("Waiting for 5 seconds...");
            System.Threading.Thread.Sleep(5 * 1000);

            Console.WriteLine("Finished.");
        }

        static void client_DataChangeNotification_Main1(object sender, EasyUADataChangeNotificationEventArgs e)
        {
            // Display value.
            if (e.Succeeded)
            {
                Console.WriteLine($"{e.Arguments.NodeDescriptor}: {e.AttributeData.Value}");
                using (StreamWriter sw = File.AppendText(OPC_Log))
                {
                    sw.WriteLine("value" + "  " + Convert.ToString(DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)));
                }
            }
        
            else
            {
                Console.WriteLine($"{e.Arguments.NodeDescriptor} *** Failure: {e.ErrorMessageBrief}");
                using (StreamWriter sw = File.AppendText(OPC_Log))
                {
                    sw.WriteLine("error" + "  " + Convert.ToString(DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture)));
                }
            }
                
        }