Can OPC Bridge connect two OPC clients directly, or does it only work between two OPC servers?
OPC Bridge is designed to transfer data between OPC servers, not between two OPC clients. The distinction matters because of how the OPC specification defines the roles of clients and servers. OPC servers expose data and respond to requests; they do not initiate communication on their own. OPC clients are the applications that read from and write to those servers. OPC Bridge acts as the client in the middle, reading from one server and writing to another.
Why OPC Servers Cannot Talk to Each Other Directly
A fundamental characteristic of the OPC architecture is that servers only respond to requests. They do not reach out to other servers to exchange data. If you have two OPC servers in your environment and you need data to flow between the controllers or systems they represent, you must introduce a client application that reads from one server and writes to the other. This is precisely the role OPC Bridge fills. Without such a client in the middle, there is no mechanism for server-to-server communication.
How OPC Bridge Sits Between Two Servers
OPC Bridge functions as an OPC client to both servers simultaneously. It subscribes to data items on the source server and writes updated values to the destination server whenever changes occur. This happens in real time and can be configured in both directions, meaning the same bridge setup can move data from Server A to Server B and from Server B to Server A within the same configuration. The bridge handles OPC DA and OPC UA servers interchangeably, so you are not limited to pairing servers of the same protocol type.
What About OPC Clients in Your Application Stack
If your question involves getting two client applications to share data, the answer typically involves ensuring both clients are connected to the same OPC server or bridging the underlying servers those clients rely on. OPC Bridge addresses the server layer, which is where the data originates. Once data is available on a target server, any OPC client can subscribe to it normally.
Relevant Tools
OPC Bridge is the feature within OPC Expert that manages real-time data transfer between OPC servers. It uses a drag-and-drop interface for configuration and supports multi-threaded operation so that a problem with one server connection does not disrupt the others. OPC Viewer, another module in OPC Expert, can be used to inspect and verify the data flowing through any connected OPC server, which is useful for confirming that a bridge is delivering values as expected.
OPC Bridge bridges servers, not clients. By acting as a client to both endpoints, it enables data exchange between systems that would otherwise be unable to communicate, solving one of the most common integration challenges in industrial automation environments.