Do not consider connection lost on some error codes

Sharp7.Rx/S7ErrorCodes.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+
+namespace Sharp7.Rx
+{
+    public static class S7ErrorCodes
+    {
+        /// <summary>
+        ///     This list is not exhaustive and should be considered work in progress.
+        /// </summary>
+        private static readonly HashSet<int> notDisconnectedErrorCodes = new HashSet<int>
+        {
+            0x000000, // OK
+            0xC00000, // CPU: Item not available
+            0x900000, // CPU: Address out of range
+        };
+
+        /// <summary>
+        ///     Some error codes indicate connection lost, in which case, the driver tries to reestablish connection.
+        ///     Other error codes indicate a user error, like reading from an unavailable DB or exceeding
+        ///     the DBs range. In this case the driver should not consider the connection to be lost.
+        /// </summary>
+        public static bool AssumeConnectionLost(int errorCode)
+        {
+            return !notDisconnectedErrorCodes.Contains(errorCode);
+        }
+    }
+}