Page tree
Skip to end of metadata
Go to start of metadata


Most of the OPC users are end users of commercially available OPC clients/servers. OPC clients/servers are usually purchased for PLCs or devices on fieldbuses which are integrated via these servers in their control systems. Users have to configure their OPC servers and their OPC clients.


It is assumed that the end user has already an OPC client installed on his machine and OPC servers installed either on this local machine or on remote machines. If not please refer to the document about installation and registration hereafter.
It is also assumed that DCOM is configured appropriately (see documents listed here after) for OPC client(s) and OPC server(s) installed on different computers. If not, problems can occur when connecting to OPC servers.

Use of an OPC client

Many free OPC clients are available for download and very usefull to quickly setup or diagnoze a Client - Server communication. Amoung them, Applicom, National Instruments, Iconics or Matrikon have developed very successful tools. Check out the OPC Client page for more information.
Matrikon in particular have produced a very nice tutorial describing the procedure for its client: Matrikon OPC explorer. A reference to this tutorial is provided in the table below. The typical procedure one has to go through is described hereafter. Old examples are provided for two OPC clients (Applicom and NI's server explorer).

  • Start the OPC client (E.g. Martikon OPC Explorer);
  • Connect to an OPC server (E.g. CAEN OPC server). If the OPC server is not running it will be launched automatically.
  • Add new OPC group(s) and optionally modify their properties;
  • Add new OPC item(s) and optionally set their properties and validate these new item(s);

The OPC items can now be accessed (read/written) from the OPC clients.If the OPC client is a SCADA system (e.g. The National Instrument BridgeView, PVSS II, Citect, Panorama, etc.), the previous procedure has to be done at configuration time. Each time the SCADA will be run, the OPC Item and groups will be automatically recreated.

If the OPC client is a "test" tool (e.g. the National Instrument Server Explorer or the Applicom OPC client) the list of created items can be saved in a file in order to be able to restore them the next time the client will be used.

Use of an OPC server

OPC servers can be seen as gateways between the OPC domain and the underlined front-end ones (e.g. fieldbus, PLC protocols, TCP/IP, etc.). Provided OPC servers are installed properly, their configuration is twofold:

  • The configuration of the accessed devices, fieldbuses or front-end computers;
  • The configuration of the OPC interface.

The first configuration is very specific of the protocol used to access the device (See the access to Profibus items from the Applicom OPC server).The configuration of the OPC part can be very simple when OPC servers are not offering any special functionality . However OPC servers may provide users with options like aliases, public group definitions, etc.

DCOM Settings for remote OPC Server - Client connection

OPC is a set of specifications based on DCOM.

Developers of OPC components will have to know details about DCOM especially if they are not using OPC toolkits.
End users of OPC components will not have to be experts in DCOM, however they will have to be able to configure the DCOM settings of their OPC servers to control the access to these servers from remote clients.

We have prepared documents to help End-users do their own configuration.

Recently the OPC Programmer Connection has gathered

on their site.

Related documents




ITCO DCOM settings

Recommended DCOM settings at CERN for Windows 2000.


ITCO DCOM settings

Recommended DCOM settings at CERN for Windows XP.


DCOM settings DCOM_Config.pdf

Recommended DCOM settings at CERN for Windows 7 and server 2008


ICONICS Dataspy OPC client


Matrikon OPC client