The OPC Server Enumerator

The OPC Server Enumerator is an application provided by the OPC Foundation make connecting an OPC client to an OPC server on a remote computer easier. This topic describes how to install the OPC Server Enumerator on a remote computer if it isn't already installed. The ApisOPCBee OPC client also uses the OPC Server Enumerator to retrieve necessary server information when connecting to a remote computer.

All OPC servers are obliged to register in the OPC servers component category on their local computer. This provides a practical way for OPC clients to retrieve all servers that are installed on that computer, they simply query the appropriate component category for all available servers. The component categories are maintained within the registry on the computer, and when the OPC server and client run on the same computer, there are no obstacles for the client to query the component categories on that computer. When the server is running on a remote computer on the other hand, the client needs help to query available servers on that computer. Therefore, OPC Foundation provided the OPC Server Enumerator.

Installing the OPC Server Enumerator

In the Apis binaries directory, e.g. C:\\Apis\Bin, there is a file called OPCENUM.EXE. Copy this file to a suitable directory on the remote computer. Then, from a Command Prompt on the remote computer, go to the directory and execute the following command:

OpcEnum /Service

Then, open DCOMCNFG.EXE located in the Windows system directory, and grant "Everyone", " SYSTEM", and "NETWORK" accounts "Access and Launch" rights to the OpcEnum application. Also, ensure that the "Enable Distributed COM on this computer" check box is checked.

OPC Server Enumerator is now installed, and you can test it by launching an application named ENUMTEST.EXE located in the Apis binaries directory. Using ENUMTEST, specify a remote server type by entering R, then enter the remote server name or IP-address to try to retrieve the OPC servers on that remote computer.