What is opcclient?

as above

When it is necessary that the "ScadaBR" communicate with a device that uses an unsupported protocol, we can install an OPC server, it works with a translator, there are several, one for each different protocol, not for everyone yet, but for the majority. For example, if you report the "ScadaBR" with a KNX equipment, "ScadaBR" will not be able to communicate, then you install an OPC server to communicate with the equipment and "ScadaBR" will work with an OPC client, only communication with the server. This needs to go into "datasource" and add a OPC communication. The OPC server will ask for the data KNX equipment and will provide these data to the ScadaBR. The ScadaBR will write data to the OPC server and OPC server will write the data into the KNX equipment. 
In this case the ScadaBR is working with an OPC client.
Look this OPC servers,
Engineer Fabio Durão