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'Command not valid unless logged in' gets returned if Ethernet to Modbus Plus bridge connection is disrupted.

Goals and Symptoms

'Command not valid unless logged in' gets returned if Ethernet to Modbus Plus bridge connection
is disrupted.

Facts and Changes

All version of ProwORX 32 and NxT

Causes and Fixes


There is a known issue when communications is disrupted when using TCP/IP to connect
'ProWORX 32' or 'ProWORX NxT' to the PLC, Attempts to try to perfom an online operation after the
disruption has been corrected, will cause the error 'Command not valid unless logged in' to be returned.
The reason is due to the fact that 'ProWORX 32' opens a TCP/IP connection and re-uses the same
connection for the communications while it is connected in the Online or Combined mode. When the
communications problem is corrected, there is still a hanging TCP/IP connection open on the PC side
that 'ProWORX 32' is using. Since 'ProWORX 32' is unaware of the TCP/IP disruption on the device
(i.e., NOE module, Ethernet to Modbus Plus bridge) which never sent a reset command, it still tries to
re-use the same connection. The only way to correct this problem is to go Offline and go back Online
to the PLC which tells 'ProWORX 32' to close the old TCP/IP connection and open a new TCP/IP
connection.

An OPR is outstanding to get this problem fixed in 'ProWORX 32'. The problem will not be fixed in
'ProWORX NxT' because it is obsolete and has been end of lifed.

To resolve the problem, It is recommended that you check the Modbus Plus and Ethernet network to
see what is causing this problem.

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