How does OPC Expert’s OPC Tunneler securely bridge OPC DA servers across firewalled networks, and how does it compare to native OPC UA communication?
OPC Tunneling Across Firewalled Networks vs. Native OPC UA
OPC Expert’s Tunneler wraps OPC communication in a standards-based transport layer, allowing data to pass through firewalls using a single configurable port rather than the dynamic port ranges that DCOM requires. This approach resolves the most common obstacle to cross-network OPC DA connectivity: firewall configurations that block DCOM callbacks or that cannot accommodate dynamic port allocation.
How the Tunneler Works
The Tunneler runs on both the machine hosting the OPC server and the machine where the OPC client resides, or in a half-tunnel configuration, it can run on just one end. It encapsulates OPC communication within OPC UA or standard TCP/IP transport, converting the underlying protocol as needed and directing all traffic through a single port. This dramatically simplifies firewall rule management because network administrators only need to open one port rather than a range of dynamic DCOM ports. The Tunneler also supports optional encryption using 128-bit or 256-bit AES, protecting data against interception as it traverses the network.
Comparison to Native OPC UA Communication
Native OPC UA is a modern, self-contained protocol that was designed from the beginning to work across networks. It uses TCP by default with configurable port assignments and includes built-in security through the OPC UA security model, which covers authentication, authorization, and message encryption. OPC UA does not rely on DCOM at all.
OPC tunneling with OPC Expert serves a different purpose. It is primarily intended for environments where OPC Classic DA servers exist and cannot be replaced or upgraded to OPC UA, but the data from those servers must be made accessible across a network boundary. The Tunneler creates a bridge that lets legacy OPC DA systems communicate as if they were on the same local network, while the actual transport is handled securely and efficiently across the firewall.
When to Use Each Approach
If your environment uses OPC UA endpoints on both ends, native OPC UA communication is the cleaner and more direct choice. If you are connecting to OPC DA servers, or if you need bidirectional DA-to-UA conversion across a network boundary, the Tunneler provides the path forward without requiring changes to the source systems. The Tunneler also supports conversion between OPC DA and OPC UA, so an OPC UA client can consume data from a legacy OPC DA server through the tunnel.
Relevant Tools
OPC Expert (OPC Tunneler): Handles DCOM-free, single-port OPC communication across firewalled networks with optional encryption and support for both half-tunnel and full-tunnel configurations.
OPC Expert (OPC Viewer): Useful for validating the tunneled connection and verifying that data is flowing correctly before or after the tunnel is established.
OPC tunneling with OPC Expert fills a specific gap in industrial network architecture: connecting legacy OPC DA systems to modern clients across security boundaries without reconfiguring the source servers or opening broad firewall exceptions.