Streamlines OPC connectivity through the Microsoft .NET API

See purchasing information for more details
Download Free Demo

Product Overview

Between June 1, 2020 and August 30, 2020, ClientAce will be transitioned into an End-of-Life phase for the product. Read the Notification Letter for more details about additional timing.  Questions and concerns can be reviewed by referring to the End-of-Life FAQ document in the Knowledgebase.  Alternatively, you may contact your Kepware Preferred Distributor or Kepware Sales contact for further clarification.

About ClientAce
OPC-enable your .NET applications with ClientAce. ClientAce provides a drag-and-drop interface to quickly and easily attach OPC items to any property or custom control built in Visual Studio. Furthermore, its full-featured .NET API provides effortless access to OPC UA, OPC DA, and OPC XML-DA server applications without previous knowledge of the OPC standard.


DA Junction Control

The DA Junction control is a customized .NET control that enables Visual Basic .NET and C# programmers to easily develop OPC client applications that access any OPC UA, OPC DA, and XML-DA servers. No detailed knowledge of OPC interfaces is required. The DA Junction will perform the connection handling procedure between your custom client application and the OPC server, as well as monitor and reconnect when necessary.

DA Junction Features:

  • The component completely covers the connection handling procedure for one or multiple OPC servers.
  • Conversion of OPC data from different OPC Data Access interfaces into .NET data types.
Server Browser Control

The Server Browser control provides functionality to browse OPC Data Access servers on local and remote machines. The Server URL is returned in an event to be used in the application for establishing connections and data acquisition.

Item Browser Control

The Item Browser control provides functionality to browse tags/items in an OPC Data Access server on local or remote machines. Items/tags are selected and their information is returned to the application. The selections are used to request updated data from the server.

Channel Settings Control

The Channel Settings control provides functionality to view and make certain changes to the properties of a channel and devices within an OPC server provided by Kepware. The ability to write to system-level tags must be enabled in the server.

Server State Control

The Server State control provides functionality to view the properties of a Kepware OPC server project. The properties include the number of clients connected to the server, the total number of tags added by the clients, and the total number of tags that are actively being polled.

ClientAce .NET API

The ClientAce .NET Application Programming Interface (API) provides users of languages such as C# and Visual Basic .NET with a simple, intuitive and optimized class library to quickly develop OPC client applications for accessing OPC servers.

API Features:

  • A simple, intuitive .NET interface.
  • The OPC UA, DA, and XML-DA interfaces have been simplified down to the major functions.
  • No detailed knowledge of the different OPC interfaces is required.
  • The API covers the different base technologies of OPC, for example, COM and DCOM.
  • The API completely covers the connection handling to one OPC Server.
  • The development of OPC Client applications with C# or Visual Basic .NET becomes very simple using ClientAce.
  • Conversion of OPC data from different OPC Data Access interfaces into .NET data types.
  • Fast and simple search for OPC COM Servers, both local and remote.
  • High performance and optimized Client-Server communication by using kernel functionality implemented in C++.
  • Design-time license per development seat
  • Unlimited applications with each license, per development seat
  • First year of Support and Maintenance is required for ClientAce purchases
  • Applications are subject to a 1-hour demo timeout (with reminder pop-ups)
  • After purchase of a license, the application can be signed to avoid the timeout & pop-ups
  • The signing utility is included with ClientAce
Free Tools With ClientAce Install
  • C# and VB.NET sample client applications
  • 1-hour demo


Available Languages

  • English

Release Notes



  • Updated the ClientAce binaries to version
  • Added support for Visual Studio 2013 IDE.
  • Added the following new examples:
    • Simple ClientAce OPC DA VS2010-12 Event Example_VB
    • Simple ClientAce OPC DA VS2010-12 Event Example_CS
    • Complex ClientAce OPC DA VS2010-12 Example_VB
  • Tested support for the .NET 4.5 Framework.
  • Added installer and files for the Visual Studio 2010 C++ Runtime and OPC Foundation Core redistributables.

ClientAce Binaries

  • Corrected an error that caused AsyncWrite to sporadically throw IndexOutOfBounds exceptions.
  • Corrected an error that caused OPC UA Connect to hang when the targeted server either did not support or had not enabled the security settings specified in the ConnectInfo object.
  • Fixed the ReadCompleted and WriteCompleted callback functions so that they return results for each item even if there is a timeout while performing the Read or Write actions (or if the complete operation failed).
  • Added the new status code E_Timeout.


  • Added support for the .NET 4.0 Framework in Visual Studio 2010 and Visual Studio 2012.
  • Added support to the ClientAce API that allows ClientAce applications to be developed as OPC UA Clients (for DA Information Models only). ClientAce supports all OPC UA security levels, direct connections to endpoints, and browsing for endpoints via Local Discovery Servers.
  • Added support to the DA Junction that allows users to connect to OPC UA endpoints directly or to browse for local OPC UA endpoints via Local Discovery Servers.
  • Added support to the ServerBrowser Control for OPC UA server browsing via Local Discovery Servers.
  • Added support to the ItemBrowser Control for OPC UA server connection and OPC Item browsing.
  • Added support for UA user authentication through the passing of username and password credentials to the OPC UA server.
  • Updated the Kepware-specific ServerState Control. There are now two controls: one for OPC DA and one for OPC UA. The Server Project Name field was removed from the control, and the Server Project Title field was added.
  • Updated the Kepware-specific ChannelSetting Control. There are now two controls: one for OPC DA and one for OPC UA. The controls were updated to support the new channel and device properties that were added during updates to KEPServerEX V5. Newly supported fields include Pending Reads/Writes and Max Pending Reads/Writes for diagnostics, Media Level Redundancy monitoring tags, device-level diagnostics tags, Scan Modem, and Ethernet Encapsulation.
  • Added support to the ClientAce API that allows ClientAce applications to be developed as OPC XML-DA clients.
  • Made an enhancement that allows users to force ClientAce to only use the OPC 3.0 IOPCBrowse Method or the OPC 2.0 IOPCBrowseServerAddressSpace Method. In the default setting, the ClientAce API queries the OPC Server to determine the OPC specification it supports and then uses the appropriate browse method; however, some OPC servers do not properly indicate the specifications that they support.
  • Added support for the IOPCCommon::SetClientName Method. For servers that support this on the OPC interface, this method allows a client application to identify itself to the server application in addition to the ClientID. Support for IOPCCommon::SetClientName was added to KEPServerEX versions 5.7 and later.


  • Updated the libraries to version
  • Added support during installation for Roaming Profiles with remote servers. Add-in Install location is now relative to the target directory selected during installation and is visible within Visual Studio's Add-in Options. Some users may be required to uninstall the product before upgrading to remove any Add-ins previously installed in the default location.
  • Added new properties to the ConnectInfo class that support configurable timeouts for UA Service calls and adding read/write groups with active items.
  • Updated DA Junction control to sample at the same rate as the publishing interval instead of sampling as fast as possible.
  • Fixed an issue where the revised update rate was not set when creating a subscription on an underlying OPC UA server.
  • Corrected an error causing an exception when removing a server through the ServerBrowser control.
  • Fixed a memory leak with applications using the asynchronous methods ReadAsync / WriteAsync without binding to a ReadCompleted / WriteCompleted event.
  • Resolved an issue where license requests on certain operating systems (Windows 7 or higher) could not be validated.


  • Updated ClientAce binaries to address a low-level threading issue that could result in orphaned threads for callbacks.
  • Updated the VB .Net examples.
  • Added two new C# examples.
  • Fixed an installation issue that occurred when the user selected "Yes" in the "Disable Support for this version of Microsoft Visual Studio" prompt during the installation.


  • Added Support for Microsoft Visual Studio 2010


  • Added Support for Microsoft Visual Studio 2008.
  • Added Microsoft Visual Studio 2008 ClientACE components.
  • Updated Visual Studio 2003 and 2005 ClientACE components to version V1.1.0.15. This update addresses anomaly with datatype sent by some OPC servers.
  • Added 3 Microsoft Visual Studio 2008 examples: Simple and Complex ClientAce VS2008 Examples, plus Simple ClientAce DA_Junction VS2008 Example.
  • Separated 3 Visual Studio examples into separate components and install Example only if corresponding Visual Studio is detected. For example, if only Visual Studio 2008 is detected, then only Visual Studio 2008 example will be installed.
  • Setup now requires a minimum of Microsoft Visual C# Language installed to Microsoft Visual Studio to enable adding of ClientAce Components to Visual Studio Toolbox.
  • Updated the help file for VS2008 and Vista specific requirements.
  • Updated the help file for changes in the OPC Items class, the properties are now a list array vs. an object array.
  • Update the help file with descriptions of the properties, methods, and events associated with the Server Browser, Item Browser, and DA Junction class objects.
  • Updated the help file with example code showing how to use the Server Browser, Item Browser, and DA Junction in a project.
  • Updated the License utility with new e-mail address for support rather than sales.
  • Updated the License Agreement.
  • Fixed issue where using ClientAce objects in forms that are a custom derived class cause them to fail with an exception.

Additional Tech Info

Development Environment Support

  • .NET 4.0/4.5
  • Visual Studio 2010 and higher

For information on supporting Visual Studio 2008, please contact Kepware Technical Support at +1 888-KEPWARE x211.

Hardware Requirements

Refer to Microsoft's .NET Framework hardware requirements for the version that will be used in the Visual Studio project:

  • 100 MB available disk space
  • Microsoft Visual Studio Requirements

When deploying the custom client applications created using ClientAce, the .NET Framework requirements depend on the version of Visual Studio that was used for development. For more information, refer to the "Deploying Your Client Application" topic in the ClientAce product manual.

Runtime Requirements

Visual Studio 2010 C++ Runtime Redistributables
  • Part of the low-level OPC layer for ClientAce is written using C++ in Visual Studio 2010. As such, ClientAce has a dependency on the redistributables for that version. It is important that these files be present when deploying a custom client application created using ClientAce. The installer for the redistributables can be found in the ClientAce Install folder.
OPC Foundation Core Redistributables
  • OPC DA client/server connectivity requires the OPC Foundation Core Redistributables, which are usually installed when an OPC client or server is installed to an operating system. When deploying a custom client application created using ClientAce to a PC that has never had an OPC client or server installed, the components must be installed for it to work. The installer for the OPC Foundation Core Redistributables can be found in the ClientAce Install folder.

Software Requirements

The following requirements must be met in order for the application to operate as designed:

  • Microsoft Windows operating system requirements are the same for both ClientAce and the Microsoft Visual Studio development environment that is used to develop ClientAce applications. If the operating system's requirements for the version of Visual Studio being used does not list the operating system intended for use, then ClientAce is not supported for use on that operating system.

UAC on Windows Vista and Windows 7

  • To ensure that all components function correctly in the design environment, turn UAC off on machines being used to develop applications with ClientAce.
  • UAC limits access to folders and files in the design environment, which will affect some objects in the design environment. UAC does not affect these objects in the Runtime environment.