Debugging messages
By enabling trace logging on a Modbus network you can monitor the query and response message cycle in a station’s standard
output, which results form normal data polling.
- Right-click the station in Nav tree and click Spy.The Spy Viewer opens.
- Click the stdout (standard output) hyperlink.The standard output trace log opens.
The trace log breaks out the query to show fields on separate lines, and the received (response) in a single line (in hex format).
In the case of the ModbusTCPNetwork, trace-level output shows a similar query/response message cycle from data polling, but with a slightly different format. The driver sends a 6-byte leading TCP header 000000000006 in each query, and omits the checksum byte in both sent and response messages.