Applies To:
  • CitectSCADA 5.xx, 6.xx, 7.00
  • CitectHMI 5.xx, 6.xx, 7.00

I have a CitectSCADA project that is configured to communicate to Unitronics controllers (Vision 230 with Ethernet card), using the modnet protocol. The device seems to go offline if CitectSCADA does not read from it for 5 seconds. Why is this happening?

The Unitronics controllers (Vision 230 with Ethernet card) has a TCP timeout, and the value by default is set to 5 seconds. This means that if there is no activity between the device and CitectSCADA for 5 seconds, the device will drop the connection.

The TCP timeout setting for the Unitronics controller needs to be increased to a reasonable value to prevent the device from dropping of the connection for brief periods of inactivity.


Unitronics controllers, Vision 230, Modnet, #COM