diff --git a/IOB-UT-NEXT/ToMapo.cs b/IOB-UT-NEXT/ToMapo.cs
index 776a6063..0e80d735 100644
--- a/IOB-UT-NEXT/ToMapo.cs
+++ b/IOB-UT-NEXT/ToMapo.cs
@@ -632,6 +632,11 @@ namespace IOB_UT_NEXT
         /// </summary>
         public bool UseFullId { get; set; } = false;
 
+        /// <summary>
+        /// Numero massimo di letture null prima di disconnettere il client
+        /// </summary>
+        public int maxNullRead { get; set; } = 1000;
+
         /// <summary>
         /// Base del NameSpace usato per le funzionalità di translate (parametri ACT --> SET)
         /// </summary>
diff --git a/IOB-WIN-NEXT/IobOpc/OpcUa.cs b/IOB-WIN-NEXT/IobOpc/OpcUa.cs
index 7cb11745..a7187c27 100644
--- a/IOB-WIN-NEXT/IobOpc/OpcUa.cs
+++ b/IOB-WIN-NEXT/IobOpc/OpcUa.cs
@@ -533,7 +533,7 @@ namespace IOB_WIN_NEXT.IobOpc
                 }
                 else
                 {
-                    lgTrace($"checkAndSend ERROR | MonIt: {MonIt.DisplayName} | NotifyValue Null!!!");
+                    lgError($"checkAndSend ERROR | MonIt: {MonIt.DisplayName} | NotifyValue Null!!!");
                 }
             }
             else
@@ -1452,7 +1452,7 @@ namespace IOB_WIN_NEXT.IobOpc
                 lgInfo($"Chiamata UAClient con configurazione standard: {application.ApplicationConfiguration.ApplicationName}");
                 string userName = opcUaParams == null || opcUaParams.Identity == null ? "" : opcUaParams.Identity.UserName;
                 string passwd = opcUaParams == null || opcUaParams.Identity == null ? "" : opcUaParams.Identity.Passwd;
-                UA_ref = new UAClient(application.ApplicationConfiguration, cIobConf.codIOB, userName, passwd, isVerboseLog, ClientBase.ValidateResponse);
+                UA_ref = new UAClient(application.ApplicationConfiguration, cIobConf.codIOB, userName, passwd, isVerboseLog, ClientBase.ValidateResponse, opcUaParams.maxNullRead);
 
                 lgInfo($"Chiamata apertura OpcUa Client: {cIobConf.cncIpAddr}:{port}");
                 UA_ref.ServerUrl = $"opc.tcp://{cIobConf.cncIpAddr}:{port}";
@@ -1594,6 +1594,8 @@ namespace IOB_WIN_NEXT.IobOpc
                             }
                         }
                     }
+                    // gestione ricezione null
+                    UA_ref.eh_nullExceed += UA_ref_eh_nullExceed;
                     // gestione eventi change
                     UA_ref.eh_MonItChange += UA_ref_eh_MonItChange;
                     lgInfo("eh_MonItChange event registered");
@@ -1614,7 +1616,7 @@ namespace IOB_WIN_NEXT.IobOpc
             // controllo read error ed eventuale disconnect
             if (readErrorCurr > readErrorMax)
             {
-                lgError($"Effettuo disconnessione x superamento errori lettura UA_ref.ReadNode, sleetp 15 sec");
+                lgError($"Effettuo disconnessione x superamento errori lettura UA_ref.ReadNode, sleep {readErrorSleepTime}msec");
                 tryDisconnect();
                 Thread.Sleep(readErrorSleepTime);
                 readErrorCurr = 0;
@@ -1622,6 +1624,20 @@ namespace IOB_WIN_NEXT.IobOpc
             return esitoLink;
         }
 
+        /// <summary>
+        /// Ricevuto troppi null --> disconnetto e traccio
+        /// </summary>
+        /// <param name="sender"></param>
+        /// <param name="e"></param>
+        /// <exception cref="NotImplementedException"></exception>
+        private void UA_ref_eh_nullExceed(object sender, int e)
+        {
+            lgError($"Effettuo disconnessione x superamento letture UA_ref.ReadNode a NULL ({e}), sleep {2 * readErrorSleepTime}msec");
+            tryDisconnect();
+            Thread.Sleep(2 * readErrorSleepTime);
+            readErrorCurr = 0;
+        }
+
         /// <summary>
         /// Formatta un dataitem x salvataggio in memoria locale
         /// </summary>
diff --git a/IOB-WIN-NEXT/UAClient.cs b/IOB-WIN-NEXT/UAClient.cs
index 1d6fc593..2d32b013 100644
--- a/IOB-WIN-NEXT/UAClient.cs
+++ b/IOB-WIN-NEXT/UAClient.cs
@@ -72,8 +72,17 @@ namespace IOB_WIN_NEXT
         /// <summary>
         /// Initializes a new instance of the UAClient class.
         /// </summary>
-        public UAClient(ApplicationConfiguration configuration, string codIOB, string user, string pwd, bool verboseLog, Action<IList, IList> validateResponse)
+        /// <param name="configuration"></param>
+        /// <param name="codIOB"></param>
+        /// <param name="user"></param>
+        /// <param name="pwd"></param>
+        /// <param name="verboseLog"></param>
+        /// <param name="validateResponse"></param>
+        /// <param name="maxNullRead">Numero massimo di risposte nulle in browsing prima di disconnettersi</param>
+        public UAClient(ApplicationConfiguration configuration, string codIOB, string user, string pwd, bool verboseLog, Action<IList, IList> validateResponse, int maxNullRead)
         {
+            currNullReceiv = 0;
+            maxNullAllowed = maxNullRead;
             m_validateResponse = validateResponse;
             currIob = codIOB;
             lg = LogManager.GetCurrentClassLogger();
@@ -99,6 +108,11 @@ namespace IOB_WIN_NEXT
         /// </summary>
         public event EventHandler<opcUaMonitItemChange> eh_MonItChange;
 
+        /// <summary>
+        /// Evento notifica superamento numero letture null
+        /// </summary>
+        public event EventHandler<int> eh_nullExceed;
+
         #endregion Public Events
 
         #region Public Properties
@@ -393,8 +407,6 @@ namespace IOB_WIN_NEXT
 
             try
             {
-                //#region Read a node by calling the Read Service
-
                 //// build a list of nodes to be read
                 //ReadValueIdCollection nodesToRead = new ReadValueIdCollection()
                 //{
@@ -427,10 +439,6 @@ namespace IOB_WIN_NEXT
                 //    lgInfo("Read Value = {0} , StatusCode = {1}", result.Value, result.StatusCode);
                 //}
 
-                //#endregion Read a node by calling the Read Service
-
-                #region Read the Value attribute of a node by calling the Session.ReadValue method
-
                 try
                 {
                     DataValue resp = m_session.ReadValue(reqNodeId);
@@ -447,8 +455,6 @@ namespace IOB_WIN_NEXT
                     numErrors++;
                     lgTrace($"ReadValue Error | reqNodeId: {reqNodeId} | numErrors: {numErrors}{Environment.NewLine}{exc}");
                 }
-
-                #endregion Read the Value attribute of a node by calling the Session.ReadValue method
             }
             catch (Exception ex)
             {
@@ -466,8 +472,6 @@ namespace IOB_WIN_NEXT
             return answ;
         }
 
-        protected int maxErrors = 20;
-
         /// <summary>
         /// Read a SINGLE of nodes value (RAW) from Server
         /// </summary>
@@ -507,8 +511,6 @@ namespace IOB_WIN_NEXT
             return answ;
         }
 
-        protected int numErrors = 0;
-
         /// <summary>
         /// Read a list of nodes from Server
         /// </summary>
@@ -618,83 +620,6 @@ namespace IOB_WIN_NEXT
                     monItList.Add(currMonIt);
                 }
 
-#if false
-                MonitoredItem IO_120_00_MonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                // Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                IO_120_00_MonitoredItem.StartNodeId = new NodeId("ns=4;s=IO_120.00");
-                IO_120_00_MonitoredItem.AttributeId = Attributes.Value;
-                IO_120_00_MonitoredItem.DisplayName = "IO_120 Variable";
-                IO_120_00_MonitoredItem.SamplingInterval = 1000;
-                IO_120_00_MonitoredItem.Notification += OnMonitoredItemNotification;
-                subscription.AddItem(IO_120_00_MonitoredItem);
-
-                MonitoredItem IO_120_01_MonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                // Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                IO_120_01_MonitoredItem.StartNodeId = new NodeId("ns=4;s=IO_120.01");
-                IO_120_01_MonitoredItem.AttributeId = Attributes.Value;
-                IO_120_01_MonitoredItem.DisplayName = "IO_120_01 Variable";
-                IO_120_01_MonitoredItem.SamplingInterval = 1000;
-                IO_120_01_MonitoredItem.Notification += OnMonitoredItemNotification;
-                subscription.AddItem(IO_120_01_MonitoredItem);
-
-                MonitoredItem IO_130_MonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                // Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                IO_130_MonitoredItem.StartNodeId = new NodeId("ns=4;s=IO_130");
-                IO_130_MonitoredItem.AttributeId = Attributes.Value;
-                IO_130_MonitoredItem.DisplayName = "IO_130 Variable";
-                IO_130_MonitoredItem.SamplingInterval = 1000;
-                IO_130_MonitoredItem.Notification += OnMonitoredItemNotification;
-                subscription.AddItem(IO_130_MonitoredItem);
-
-                MonitoredItem IO_135_MonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                // Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                IO_135_MonitoredItem.StartNodeId = new NodeId("ns=4;s=IO_135");
-                IO_135_MonitoredItem.AttributeId = Attributes.Value;
-                IO_135_MonitoredItem.DisplayName = "IO_135 Variable";
-                IO_135_MonitoredItem.SamplingInterval = 1000;
-                IO_135_MonitoredItem.Notification += OnMonitoredItemNotification;
-                subscription.AddItem(IO_135_MonitoredItem);
-
-                MonitoredItem IO_140_MonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                // Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                IO_140_MonitoredItem.StartNodeId = new NodeId("ns=4;s=IO_140");
-                IO_140_MonitoredItem.AttributeId = Attributes.Value;
-                IO_140_MonitoredItem.DisplayName = "IO_140 Variable";
-                IO_140_MonitoredItem.SamplingInterval = 1000;
-                IO_140_MonitoredItem.Notification += OnMonitoredItemNotification;
-                subscription.AddItem(IO_140_MonitoredItem);
-
-                //MonitoredItem intMonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                //// Int32 Node - Objects\CTT\Scalar\Simulation\Int32
-                //intMonitoredItem.StartNodeId = new NodeId("ns=2;s=Scalar_Simulation_Int32");
-                //intMonitoredItem.AttributeId = Attributes.Value;
-                //intMonitoredItem.DisplayName = "Int32 Variable";
-                //intMonitoredItem.SamplingInterval = 1000;
-                //intMonitoredItem.Notification += OnMonitoredItemNotification;
-
-                //subscription.AddItem(intMonitoredItem);
-
-                //MonitoredItem floatMonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                //// Float Node - Objects\CTT\Scalar\Simulation\Float
-                //floatMonitoredItem.StartNodeId = new NodeId("ns=2;s=Scalar_Simulation_Float");
-                //floatMonitoredItem.AttributeId = Attributes.Value;
-                //floatMonitoredItem.DisplayName = "Float Variable";
-                //floatMonitoredItem.SamplingInterval = 1000;
-                //floatMonitoredItem.Notification += OnMonitoredItemNotification;
-
-                //subscription.AddItem(floatMonitoredItem);
-
-                //MonitoredItem stringMonitoredItem = new MonitoredItem(subscription.DefaultItem);
-                //// String Node - Objects\CTT\Scalar\Simulation\String
-                //stringMonitoredItem.StartNodeId = new NodeId("ns=2;s=Scalar_Simulation_String");
-                //stringMonitoredItem.AttributeId = Attributes.Value;
-                //stringMonitoredItem.DisplayName = "String Variable";
-                //stringMonitoredItem.SamplingInterval = 1000;
-                //stringMonitoredItem.Notification += OnMonitoredItemNotification;
-
-                //subscription.AddItem(stringMonitoredItem);
-#endif
-
                 // Create the monitored items on Server side
                 subscription.ApplyChanges();
                 lgInfo($"MonitoredItems created for SubscriptionId = {subscription.Id}");
@@ -707,7 +632,7 @@ namespace IOB_WIN_NEXT
         }
 
         /// <summary>
-        /// Write a list of nodes to the Server 
+        /// Write a list of nodes to the Server
         /// </summary>
         /// <param name="node2Write"></param>
         public void WriteNodes(List<WriteValue> node2Write)
@@ -846,32 +771,6 @@ namespace IOB_WIN_NEXT
                 qtyWriteVal.Value.Value = (int)hhmm + 10;
                 nodesToWrite.Add(qtyWriteVal);
 
-#if false
-                //// Int32 Node - Objects\CTT\Scalar\Scalar_Static\Int32
-                //WriteValue intWriteVal = new WriteValue();
-                //intWriteVal.NodeId = new NodeId("ns=2;s=Scalar_Static_Int32");
-                //intWriteVal.AttributeId = Attributes.Value;
-                //intWriteVal.Value = new DataValue();
-                //intWriteVal.Value.Value = (int)100;
-                //nodesToWrite.Add(intWriteVal);
-
-                //// Float Node - Objects\CTT\Scalar\Scalar_Static\Float
-                //WriteValue floatWriteVal = new WriteValue();
-                //floatWriteVal.NodeId = new NodeId("ns=2;s=Scalar_Static_Float");
-                //floatWriteVal.AttributeId = Attributes.Value;
-                //floatWriteVal.Value = new DataValue();
-                //floatWriteVal.Value.Value = (float)100.5;
-                //nodesToWrite.Add(floatWriteVal);
-
-                //// String Node - Objects\CTT\Scalar\Scalar_Static\String
-                //WriteValue stringWriteVal = new WriteValue();
-                //stringWriteVal.NodeId = new NodeId("ns=2;s=Scalar_Static_String");
-                //stringWriteVal.AttributeId = Attributes.Value;
-                //stringWriteVal.Value = new DataValue();
-                //stringWriteVal.Value.Value = "String Test";
-                //nodesToWrite.Add(stringWriteVal);
-#endif
-
                 // Write the node attributes
                 StatusCodeCollection results = null;
                 DiagnosticInfoCollection diagnosticInfos;
@@ -907,6 +806,10 @@ namespace IOB_WIN_NEXT
 
         protected static bool isLogVerbose = false;
         protected static Logger lg;
+        protected int currNullReceiv = 0;
+        protected int maxErrors = 20;
+        protected int maxNullAllowed = 100;
+        protected int numErrors = 0;
 
         #endregion Protected Fields
 
@@ -1002,12 +905,32 @@ namespace IOB_WIN_NEXT
                 // Log MonitoredItem Notification event
                 MonitoredItemNotification notification = e.NotificationValue as MonitoredItemNotification;
 
-                // sollevo evento notifica vaziazione MonitoredItem
-                if (eh_MonItChange != null)
+                // verifico se ricevo null, superata soglia genero eccezione
+                if ($"{notification.Value}" == "(null)")
                 {
-                    eh_MonItChange(this, new opcUaMonitItemChange(monitoredItem, notification));
+                    currNullReceiv++;
+                }
+                else
+                {
+                    currNullReceiv--;
+                    currNullReceiv = currNullReceiv > 0 ? currNullReceiv : 0;
+                    // sollevo evento notifica vaziazione MonitoredItem
+                    if (eh_MonItChange != null)
+                    {
+                        eh_MonItChange(this, new opcUaMonitItemChange(monitoredItem, notification));
+                    }
                 }
                 lgTrace($"Notification Received | Variable: {monitoredItem.DisplayName} | Value: {notification.Value}");
+                // se ho ricevuto troppi nul --> disconnetto
+                if (currNullReceiv > maxNullAllowed)
+                {
+                    if (eh_nullExceed != null)
+                    {
+                        eh_nullExceed(this, currNullReceiv);
+                    }
+                    // reset
+                    currNullReceiv = 0;
+                }
             }
             catch (Exception ex)
             {