plc4j(ab-eth): Fix read tag after refactoring/spi3 (#2606)

plc4j/drivers/ab-eth/src/main/java/org/apache/plc4x/java/abeth/AbEthMessageCodec.java

diff --git a/plc4j/drivers/ab-eth/src/main/java/org/apache/plc4x/java/abeth/AbEthMessageCodec.java b/plc4j/drivers/ab-eth/src/main/java/org/apache/plc4x/java/abeth/AbEthMessageCodec.java
index d99e63b..a20dda2 100644
--- a/plc4j/drivers/ab-eth/src/main/java/org/apache/plc4x/java/abeth/AbEthMessageCodec.java
+++ b/plc4j/drivers/ab-eth/src/main/java/org/apache/plc4x/java/abeth/AbEthMessageCodec.java
@@ -68,8 +68,8 @@
 
     @Override
     protected int calculateTotalMessageSize(byte[] header, int availableBytes) throws MessageCodecException {
-        // Little-endian unsigned 16-bit at offset 2
-        int payloadLength = (header[LENGTH_OFFSET] & 0xFF) | ((header[LENGTH_OFFSET + 1] & 0xFF) << 8);
+        // Big-endian unsigned 16-bit at offset 2
+        int payloadLength = ((header[LENGTH_OFFSET] & 0xFF) << 8) | (header[LENGTH_OFFSET + 1] & 0xFF);
         return payloadLength + HEADER_OVERHEAD;
     }