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I have Freezing problem at Telvent HU-AF.

murat

I am using telvent RTU and Power Scada a Project. But between RTU with Power Scada is disconnecting communication at different time (for example 3 day or 1 week or 3 week). Communication protocol is modbus tcp/ip. RTU have two port; port1 for server 1, port2 for server2. 

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  • This is how I interpret the wireshark logs:

    # Server 1:

    Communication looks OK; all Modbus requests get a response and TCP-connection stays up

    # Server 2:

    1. TCP communication is set up from Citect side; lines 2, 3 and 4 show normal SYN, SYN/ACK, ACK handshake so RTU is able to have more than 1 TCP connection
    2. Citect sends a Modbus READ command and the RTU responds to that according to lines 5 to 8. I cannot see what kind of response though, it could also be an error message
    3. Citect does not send any further Modbus requests
    4. After 50 seconds of no TCP communication the RTU closes the TCP connection (lines 9 to 11 show FIN, ACK, RST/ACK); looks like normal time-out behaviour of the RTU
    5. Process repeats itself

    Conclusion:

    - Standby Citect server still tries to communicate to the RTU periodically. This could be the watchdog mechanism Stuart mentioned before. So, did you follow any of the recommendations that Olivier and Stuart have given yet? Are your IODevices in Exclusive mode and/or did you set the [IOServer]Watchdog=0 parameter on both servers while you performed the WireShark tests?

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  • This is how I interpret the wireshark logs:

    # Server 1:

    Communication looks OK; all Modbus requests get a response and TCP-connection stays up

    # Server 2:

    1. TCP communication is set up from Citect side; lines 2, 3 and 4 show normal SYN, SYN/ACK, ACK handshake so RTU is able to have more than 1 TCP connection
    2. Citect sends a Modbus READ command and the RTU responds to that according to lines 5 to 8. I cannot see what kind of response though, it could also be an error message
    3. Citect does not send any further Modbus requests
    4. After 50 seconds of no TCP communication the RTU closes the TCP connection (lines 9 to 11 show FIN, ACK, RST/ACK); looks like normal time-out behaviour of the RTU
    5. Process repeats itself

    Conclusion:

    - Standby Citect server still tries to communicate to the RTU periodically. This could be the watchdog mechanism Stuart mentioned before. So, did you follow any of the recommendations that Olivier and Stuart have given yet? Are your IODevices in Exclusive mode and/or did you set the [IOServer]Watchdog=0 parameter on both servers while you performed the WireShark tests?

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