OPC Configuration

VTScada supports both OPC UA and OPC Classic.

The OPC UA Client driver interfaces to an OPC UA server running on either the local or another computer.

OPC UA is an alternative communication protocol to OPC CLASSIC, which uses DCOM for communication between a client and a server.

As DCOM is not involved in OPC UA, fewer steps are required to configure a connection to a server, successfully. DCOM for OPC CLASSIC has a reputation for being difficult to configure, so much so that a number of commercial "OPC-tunnellers" exist that act as proxies between the client and server in an effort to simply the configuration.

An OPC UA server may be running on a remote computer or be embedded in a smart device. It can run on a variety of operating systems (e.g. Windows, Linux etc). The number of OPC UA products available is still limited, while there are many OPC CLASSIC servers still available and already deployed. Here also, a tunneller can be used to connect OPC UA clients to an OPC CLASSIC server.

If both client and server are using OPC UA, the only additional configuration necessary is to ensure that firewalls allow the correct ports to be opened. The port(s) in use are defined by the OPC UA server.

For most tags, only the value is available directly. Driver tags contain seven variables in addition to the value. (Communication Driver Log-Enabled Variables) Other variables and properties can be monitored by creating an expression in an I/O and Calculations tag to mirror that variable, then publishing the calculation tag. For an example, refer to: Monitor the Alarm Status