Merge branch 'dev'

Apollo3zehn · Nov 17, 2022 · 40b6a56 · 40b6a56
2 parents 2485395 + 24317f5
commit 40b6a56
Show file tree

Hide file tree

Showing 3 changed files with 60 additions and 6 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,8 +1,14 @@
+## v5.0.2 - 2022-11-14
+
+### Bugs Fixed
+
+- The Modbus RTU client did not correctly detect response frames (thanks @zhangchaoza, fixes https://github.com/Apollo3zehn/FluentModbus/issues/83)
+
 ## v5.0.1 - 2022-11-14
 
 ### Bugs Fixed
 
-- The Modbus server did not correctly detect request frames (thanks @jmsqlr, https://github.com/Apollo3zehn/FluentModbus/pull/75#issuecomment-1304653670)
+- The Modbus RTU server did not correctly detect request frames (thanks @jmsqlr, https://github.com/Apollo3zehn/FluentModbus/pull/75#issuecomment-1304653670)
 
 ## v5.0.0 - 2022-09-08
 

diff --git a/src/FluentModbus/ModbusUtils.cs b/src/FluentModbus/ModbusUtils.cs
@@ -111,7 +111,9 @@ public static bool DetectRequestFrame(byte unitIdentifier, Memory<byte> frame)
 
         public static bool DetectResponseFrame(byte unitIdentifier, Memory<byte> frame)
         {
-            /* Correct response frame (min. 6 bytes)
+            // 
+
+            /* Response frame for read methods (0x01, 0x02, 0x03, 0x04, 0x17) (min. 6 bytes)
              * 00 Unit Identifier
              * 01 Function Code
              * 02 Byte count
@@ -120,6 +122,17 @@ public static bool DetectResponseFrame(byte unitIdentifier, Memory<byte> frame)
              * 05 CRC Byte 2
              */
 
+            /* Response frame for write methods (0x05, 0x06, 0x0F, 0x10) (8 bytes)
+             * 00 Unit Identifier
+             * 01 Function Code
+             * 02 Address
+             * 03 Address
+             * 04 Value
+             * 05 Value
+             * 06 CRC Byte 1
+             * 07 CRC Byte 2
+             */
+
             /* Error response frame (5 bytes)
              * 00 Unit Identifier
              * 01 Function Code + 0x80
@@ -130,10 +143,12 @@ public static bool DetectResponseFrame(byte unitIdentifier, Memory<byte> frame)
 
             var span = frame.Span;
 
+            // absolute minimum frame size
             if (span.Length < 5)
                 return false;
 
-            if (unitIdentifier != 255) // 255 means "skip unit identifier check"
+            // 255 means "skip unit identifier check"
+            if (unitIdentifier != 255)
             {
                 var newUnitIdentifier = span[0];
 
@@ -142,8 +157,41 @@ public static bool DetectResponseFrame(byte unitIdentifier, Memory<byte> frame)
             }
 
             // Byte count check
-            if (span[1] < 0x80 && span.Length < span[2] + 5)
-                return false;
+            if (span[1] < 0x80)
+            {
+                switch (span[1])
+                {
+                    // Read methods
+                    case 0x01:
+                    case 0x02:
+                    case 0x03:
+                    case 0x04:
+                    case 0x17:
+
+                        if (span.Length < span[2] + 5)
+                            return false;
+
+                        break;
+
+                    // Write methods
+                    case 0x05:
+                    case 0x06:
+                    case 0x0F:
+                    case 0x10:
+
+                        if (span.Length < 8)
+                            return false;
+
+                        break;
+                }
+            }
+
+            // Error (only for completeness, length >= 5 has already been checked above)
+            else
+            {
+                if (span.Length < 5)
+                    return false;
+            }
 
             // CRC check
             var crcBytes = span.Slice(span.Length - 2, 2);

diff --git a/version.json b/version.json
@@ -1,4 +1,4 @@
 {
-    "version": "5.0.1",
+    "version": "5.0.2",
     "suffix": ""
 }