diff --git a/SCADA/Program/DataService/ExtensionMethods.cs b/SCADA/Program/DataService/ExtensionMethods.cs
index f27440d..d92cb40 100644
--- a/SCADA/Program/DataService/ExtensionMethods.cs
+++ b/SCADA/Program/DataService/ExtensionMethods.cs
@@ -1,9 +1,7 @@
 using System;
-using System.Text;
-using System.Net;
 using System.Collections.Generic;
-using System.Runtime.InteropServices;
-using System.Data.SqlClient;
+using System.Net;
+using System.Text;
 
 namespace DataService
 {
@@ -771,10 +769,12 @@ namespace DataService
 
         public static unsafe short NetToInt16(byte[] value, int startIndex)
         {
-            if (value == null || startIndex > value.Length - 2)
+            if (value == null || startIndex > value.Length)
             {
                 throw new NotImplementedException();
             }
+            if (startIndex > value.Length - 2)
+                return value[value.Length - startIndex];
             fixed (byte* numRef = &(value[startIndex]))
             {
                 return (short)((numRef[0] << 8) | numRef[1]);
@@ -783,10 +783,12 @@ namespace DataService
 
         public static unsafe int NetToInt32(byte[] value, int startIndex)
         {
-            if (value == null || startIndex > value.Length - 4)
+            if (value == null || startIndex > value.Length)
             {
                 throw new NotImplementedException();
             }
+            if (startIndex > value.Length - 4)
+                return value[value.Length - startIndex];
             fixed (byte* numRef = &(value[startIndex]))
             {
                 return (int)((numRef[0] << 24) | (numRef[1] << 16) | (numRef[2] << 8) | numRef[3]);
diff --git a/SCADA/Program/DataService/PLCGroup.cs b/SCADA/Program/DataService/PLCGroup.cs
index cea6922..c9b4e79 100644
--- a/SCADA/Program/DataService/PLCGroup.cs
+++ b/SCADA/Program/DataService/PLCGroup.cs
@@ -363,7 +363,7 @@ namespace DataService
                             ushort size = addr.DataSize;
                             for (int i = 0; i < size; i++)
                             {
-                                if (rcvBytes[iByte1 + i] != cache[iByte + i])
+                                if (iByte1 + i < rcvBytes.Length && rcvBytes[iByte1 + i] != cache[iByte + i])
                                 {
                                     _changedList.Add(index);
                                     break;
diff --git a/SCADA/Program/SiemensPLCDriver/SiemensPLCDriver.cs b/SCADA/Program/SiemensPLCDriver/SiemensPLCDriver.cs
index 36e2509..482b59f 100644
--- a/SCADA/Program/SiemensPLCDriver/SiemensPLCDriver.cs
+++ b/SCADA/Program/SiemensPLCDriver/SiemensPLCDriver.cs
@@ -784,7 +784,7 @@ namespace SiemensPLCDriver
                             ushort size = addr.DataSize;
                             for (int i = 0; i < size; i++)
                             {
-                                if (rcvBytes[iByte1 + i] != cache[iByte + i])
+                                if (iByte1 + i < rcvBytes.Length && rcvBytes[iByte1 + i] != cache[iByte + i])
                                 {
                                     _changedList.Add(index);
                                     break;
diff --git a/SCADA/dll/SiemensPLCDriver.dll b/SCADA/dll/SiemensPLCDriver.dll
index 709ceca..6ff1259 100644
Binary files a/SCADA/dll/SiemensPLCDriver.dll and b/SCADA/dll/SiemensPLCDriver.dll differ