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[Technical Inquiry] EKI-1222: How can I check the status of TCP connection?

This topic has been moved by benDOTmorgan on 2014-8-7 01:20.

EKI-1222: How can I check the status of TCP connection?

I have an EKI-1222 and a modbus/RTU device behind it as a slave.
My problem is that in case of a fault, such as a receive timeout, I cannot tell whether it is the slave that has disconnected or the TCP connection to the EKI master that has dropped.
I tried sending modbus packages to the EKI using modbus id = 1 (which is assigned to the EKI) but I never get any response from the EKI, not even a modbus exception.
If it is the TCP connection that was dropped then it must be reestablished, otherwise it shouldn't.

A good solution would be to make the EKI respond to the 'Diagnostic' modbus function like the ADAMs do.
Or at least send a modbus exception packet!

I know of course that I can detect the presence of the EKI in the
network by means of UDP ASCII commands (documentation?) but this does not tell me anything abut the existing TCP connection.

Any ideas?



No, as it stands the EKI cannot create a Modbus response on its own.  It merely transposes one kind of Modbus to the other (RTU to TCP or TCP to RTU).

Your TCP client should be able to tell a socket Closed/Disconnected state (at layer 4) apart from a Timeout of the Modbus protocol (at layer 5).

Alternatively you can use ICMP (ping) tests as a side-band method of seeing if the EKI is available on the Ethernet network.


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