Hello, I am writing to inquire about a connection issue between KEPServerEX and the CIMON OPC UA Server.
Currently, I can successfully connect to the CIMON OPC UA Server using both UaExpert and Node.js (node-opcua library).
However, when attempting to connect to the CIMON OPC UA Server via KEPServerEX, I encounter a BadTcpMessageTooLarge error.
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Current Situation
CIMON OPC UA Server Details
- IP: [CIMON_IP]
- Port: 4840
- Security Policy: None
- Message Security Mode: None
UaExpert Connection
- Successfully connects to the CIMON OPC UA Server, allowing node browsing and data reading.
Node.js Connection
- Successfully connects to the CIMON OPC UA Server, enabling data read/write operations.
KEPServerEX Connection
- Using the OPC UA Client Driver, attempting to connect to the CIMON OPC UA Server results in a BadTcpMessageTooLarge error.
- Wireshark packet analysis shows that after sending a GetEndpointsRequest, the CIMON OPC UA Server returns this error.
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Wireshark Request Packet Comparison
UaExpert Request Packet:
- Message Size: 98 bytes
- Details:
- EndpointUrl: opc.tcp://[CIMON_IP]:4840
- LocaleIds: None (ArraySize: 0)
- ProfileUris: None (ArraySize: 0)
KEPServerEX Request Packet:
- Message Size: 167 bytes
- Details:
- EndpointUrl: opc.tcp://[CIMON_IP]:4840
- LocaleIds: None (ArraySize: 0)
- ProfileUris: 1 URI included (http://opcfoundation.org/UA-Profile/Transport/uatcp-uasc-uabinary)
TCP Segments Comparison:
- UaExpert Request: Sent in a single TCP segment.
- KEPServerEX Request:
- Reassembled TCP Segments:
- Frame #101: 12 bytes
- Frame #102: 4 bytes
- Frame #103: 151 bytes
- Total Length: 167 bytes
- It seems the CIMON OPC UA Server might have trouble handling segmented TCP packets from KEPServerEX.
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Comparison Results
- KEPServerEX’s request is slightly larger due to the inclusion of ProfileUris.
- However, 167 bytes is not typically considered a "large message" in OPC UA communications.
- UaExpert successfully handles requests larger than 167 bytes without issues.
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Steps Taken to Resolve
Network Connection
- Ping and TCP connection tests confirm accessibility (Port 4840).
KEPServerEX Configuration
- Configured with Security Policy: None, Message Security Mode: None.
Wireshark Analysis
- Compared request message size and TCP segments between UaExpert and KEPServerEX.
- KEPServerEX’s request is sent in multiple TCP segments, which might not be properly handled by the CIMON OPC UA Server.
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