Received packet is unknown

What does ERR_BAD_PACKET_RECEIVED mean?

The Modbus TCP server received a packet that it could not identify or parse. This indicates a received packet that does not correspond to any known Modbus TCP frame type or supported protocol, often due to incorrect protocol or malformation.

• Non-Modbus TCP traffic directed to the Modbus TCP port (default 502).
• Severely malformed or corrupted packets that cannot be recognized.
• Unsupported Modbus function codes or protocol extensions being used by the client.

Click steps to track your progress.

1. 1

   Verify that only Modbus TCP traffic is being sent to the controller's Modbus TCP port (default 502).

2. 2

   Check the remote Modbus TCP client for configuration errors that might send incorrect packet types.

3. 3

   Use a network protocol analyzer to inspect the unknown packet contents and determine their origin.