Connection dropping out on Modbus TCP

Submitted by hanky on Mon, 01/25/2010 - 03:15
in

G'day,
i have recently purchased V1.2 of the ScadaMobile app for the iphone and i am finding the TCP connection to the PLC keeps losing itself every time i try to write a value. The value gets changed in the PLC but then all the tags in ScadaMobile go blank and it loses its conneciton.

This occurred with an extremely simple network with only the iPod touch, wifi router and a Schneider Electric plc. I ran a wireshark trace on a port mirror of the PLC's connection and saw lots of duplicate ACK's and loss of connections.

Is there going to be an update soon to the app to make this more reliable as i think the concept is fantastic? Also, a feature suggestion would be to be able to address booleans as bits in a word, eg HR6000.12 as a boolean. This would make this app even more useful.

Cheers, and keep up the fantastic work.

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Hi hanky. This is a known

Submitted by Joan on Mon, 01/25/2010 - 10:18.

Hi hanky.

This is a known issue that affects 1.2.1 and 1.2.2 for certain modbus devices. The problem is due to a bug in the App that expects the response of a write operation when a previous read is not completed. This wrongly triggers a disconnection. The issue was solved and incorporated in version 1.3 which was sent to Apple for review last week and should be available for download on the App Store soon. Apple usually takes one to three weeks to review an upgrade, so it might be out this week.

Joan.
SweetWilliam Support

Fixed

Submitted by hanky on Mon, 02/01/2010 - 02:09.

G'day,
just though id let you know i got version 1.3 today and its fantastic. The modbus issue is gone and it all works great.
Cheers