From OpenSCADAWiki
We will create an object for the controller to acquire on the protocol ModBus/TCP and get this data. Thus, we actually realise the task of acquisition real data since our configuration will differ from working with real external device only with its address and the addresses of the ModBus registers, and that may also be another physical interface of the interaction — variant of the protocol ModBus. This connection is also a bright example of the ability to implement a data source environment (PLC) based on OpenSCADA.