Tunneling of OPC DA data

The networking protocol for OPC DA is DCOM. DCOM is difficult to configure, responds poorly to network interruptions, produces high network traffic, and has significant security weaknesses.

OPC DA tunneling applications are designed to overcome these limitations when using OPC DA over a network. The goal of OPC DA tunneling is to eliminate DCOM by replacing it with a network protocol like TCP. Instead of connecting the OPC DA client to a networked OPC DA server, the client program connects to a local OPC DA tunneling application, which acts as a local OPC server. The tunneling application accepts requests from the OPC DA client and converts them to TCP messages, which are then sent across the network to a companion tunneling application on the OPC DA server computer. There the request is converted back to OPC DA and is sent to the OPC DA server application for processing. Any response from the server is sent back across the tunnel to the OPC DA client application in the same manner.

Diagram: OPC DA data is sent over the network by OPC DA tunneler using common network protocols.

OPC DA tunneling products are available from several vendors, including Kepware and Matrikon.

When selecting OPC DA tunneling applications, look for products that

• keep the synchronous OPC DA transactions local to the client and server, with an asynchronous tunnel connection
• provide link monitoring
• handle network disruptions effectively
• meet your security needs