OPCDA.NET, OPC HDA .NET, DA server converting one Xi server, OPC DA Server-Side XML Gateway

OPC Classic for .NET

 

.Net OPC Solutions

 

Sub CategorySummary
Client Components

A wrapper layer is required for .Net client applications to be able to access OPC servers. Advosol offers such wrapper software components for OPC DA, HDA, A&E and XML-DA clients.



Server Development Kits

OPC DA servers can be developed with .Net tools. No COM and COM Interop knowledge is required. A device access customization module with a simple interface to the generic OPC server is coded in C# or VB.Net.
This OPC server development approach is specially suited for servers that front-end a data base or have TCP/IP or serial communication to the device.

Servers and Tools

The products in this category are for end user. Most other Advosol products are components and toolkits for the software developer.

 


Please select a subcategory above

 

Category Description
.Net OPC Solutions

OPC is based on the Windows OLE/DCOM technology and has brought standardization to thousands of applications. Now most new applications are developed on the .NET base and require support for the OPC standard in .NET, including COM interop, web services and access to existing COM based OPC solutions.

Advosol offers the most complete set of .NET components and tools for the software developer and system builder. We have decades of experience developing and selling software components and know what it takes to for the user to achieve maximum cost savings:

  • Robust, full featured, efficiently coded and well tested software
  • Comprehensive documentation, guides and samples
  • Tools for development, testing and deployment
  • Support for the component usage and it's interaction with other components

All our products are OPC compliance tested and include tools, wizards, samples, documentation and free support.

Overview OPC web services, OPC .Net, OPC Linux

 

OPC .NET Product Overview
Advosol Inc. offers the most complete .NET support with .Net Wrappers for the OPC client development, Server Toolkits with .Net customization module and OPC-XML gateways.

 

 
DA V2 / V3
A & E
HDA
XML DA
Client Components
Server Tools

 

 

Advosol offers software components and tools that makes the combination of OPC and .NET real simple.

 

.Net OPC Clients>The client development components allow .Net client applications to access OPC servers. These software packages are much more than simple .Net wrapper. They provide everything needed for efficient application development. All OPC defined functions can be called through easy to use classes with all data properly converted. Additional software layers offer a number of higher level functions like browsing the server supported items into a .Net TreeNode structure. Visual Studio project and class generation wizards make usage simple and quick. The Visual Studio integrated help offers context sensitive help.
OPC DA .NET Client ComponentOPCDA.NET offers highly efficent and flexible access to OPC DA V2/V3 servers.
On-For-All .NET Client ComponentXMLDA.NET supports access to OPC DA V2/V3 and XML DA servers. The clients are developed as XML DA clients, independent of the type of server.
OPC HDA .NET Client ComponentOPCHDA.NET handles access to OPC HDA historian servers and can be used in combination with OPCDA.NET and OPCAE.NET.
OPC AE .NET Client ComponentOPCAE.NET handles access to OPC Alarm and Events servers and can be used in combination with OPCDA.NET and OPCHDA.NET.

.Net OPC ServersThe .NET server toolkits have an OPC standard compliant generic COM server and a .NET wrapper that allows the application specific server functionaly to be implemented with VB.Net/C# as a .NET assembly.

OPC DA .NET Server Toolkit  The DANSrv is an OPC DA V2.05 / V3.0 compliant server that can be customized in .Net assembly. OPC servers that e.g. front-end a database or an Ethernet connected device can take advantage of the .Net tools. A simple .Net assembly has to be created, no COM and OPC knowledge is required.
The customization assembly can also be used with the XML-DA Customizable server. No further effort is required to support the new OPC XML-DA standard.
OPC Historian .NET Server ToolkitThe HDANSrv includes full source code of compliance tested sample servers.
OPC HDA servers can be implemented in C# or VB.Net.

 

How to develop OPC DA Servers today?

 

If you have to develop a new OPC server today then you have to make a basic decision: Should the development be done on the legacy DCOM technology or the current .NET and XML Web Services base?
Because there are thousands of OPC DA applications but yet only a few OPC web service applications you may have to decide for an OPC DA DCOM server, well knowing that you invest into a legacy technology and soon will have to invest again to support the new standards.

 

OPC .Net Server and OPC DA Server

 

Advosol offers components that actually prevent having to make such a decision. You can develop an OPC server as a .Net assembly using Visual Basic or C# and run it as an OPC DA or XML DA server.
As it is common in OPC server toolkits, the Advosol server toolkits implement the OPC specification in a generic server part and the user only has to supply a .Net assembly with the device access functions. This .Net assembly doesn't use any COM features, is multi-threaded and doesn't have the limitations of an ActiveX based solution.

 

How to develop OPC DA Clients today?

The DCOM base of OPC is declared a legacy technology and Microsoft bases new developments on .Net and web services. Developers of OPC client applications follow this trend rather quickly and new OPC clients are likely developed as .Net applications. Most devices installed today however, have DCOM based OPC DA V2 servers. Devices that need to be accessed remotely are likely to have OPC XML-DA servers based on the web services technology.
This means that clients currently mostly access OPC-DA servers but will soon have to be able to access XML-DA servers.

There are fundamental differences between OPC-DA and XML-DA servers, but a wrapper layer can hide these differences as long as performance is not an issue. To achieve high performance the wrapper layer has to be minimized and therefore the client has to be designed to match the structure of the server. Advosol supports these requirements with two OPC DA wrapper products, OPCDA.NET is optimized for OPC-DA server access and XMLDA.NET is optimized for XML-DA.
See OPC-DA / XML-DA Comparison for an overview and comparison of the two OPC specifications.


There are different ways to develop .Net OPC clients for access to OPC-DA servers:

 


.Net Interop Services

Microsoft provides COM Interop Services in the .Net Framework that allow a .Net application to access COM servers.
Best documented is the access to Automation objects. With OPC servers this means that access has to go through the Automation wrapper, resulting in a .Net wrapper on top of the Automation wrapper. The additional layer adds an additional interface that lowers the performance and increases the potential for problems if parts of the software are updated.
To access OPC servers, many type conversions have to be correctly implemented. Be prepared to spend quite some time if you do this the first time.



 

.Net Wrapper Product>

OPC .Net Wrapper, OPC DA Client, OPC .Net Client Component

Commercial wrapper products that handle all type conversions are available at low costs. They solve the .Net wrapping but are proprietary solutions because there is not yet a OPC .NET API specified.
Advosol's OPCDA.NET is such a wrapper. It is optimized for top performance and offers additional features such as wizards and context sensitive help to simplify and quicken the application development.
OPCDA.NET offers a .Net API that is modeled after the OPC DA interface and offers high performance, faster than the OPC DA Automation interface in a conventional C++ application.

 

 


XML-DA Wrapper

If performance is not paramount then a more complex wrapper can be used. The client application can be implemented as an XML-DA client and as such can directly access the soon to be more widely available XML-DA servers.
Such a client can access OPC DA servers in two ways:

XML-DA to OPC-DA Gateway

XML-DA Gateway, OPC XML, OPC DA Server, OPC XML Client >

The XML-DA client accesses the OPC-DA server through an XML-DA gateway server, which is installed at the location of the OPC-DA.
When an XML-DA server gets available the client can access it directly, eliminating the need for the gateway server.
This is not a highly efficient solution but it supports access to remote OPC DA servers and is readily available for use with any OPC server.

XMLDA.NET Wrapper

OPC XML DA Client, OPC XML DA Server, OPC DA Server, OPC .Net Wrapper

XMLDA.NET is a .Net assembly DLL with the same interface as an XML-DA .Net Web Service. It wraps the client calls to OPC DA server calls without going through XML serialization, achieving much better performance. If the client application is implemented as an ASP web application then remote access is possible on application level and the ASP application can be installed at the location of the OPC DA server.

A client application that references the XMLDA.NET assembly in place of an XML-DA web service can access multiple OPC-DA and XML-DA servers by specifying either a COM server ProgId or a web service URL.

To change an XMLDA.NET based client into a pure XML-DA client only the XMLDA.NET assembly reference needs to be replaced by an XML-DA web service reference.

 

 

 

Benchmarks

The following benchmark data was measured in a C# .Net Windows Form application.
One item is read from OPC-DA and XML-DA servers using different wrappers and gateways.
The absolute times depend on the computer and could be 5 times faster on a top end PC. Interesting is mainly the relative performance of the different access methods.

 

 

Client with
OPCDA.NET Wrapper
XML-DA Client with XMLDA.NET
XML-DA web services client
read<pollread / poll
OPC DA Server
0.58 ms
10 ms
0.07 ms
 
local XML-DA Gateway to local OPC DA Server
 
45 ms
<35ms 
45 ms / 35 ms
local XML-DA Server
 
35 ms
35 ms
35 ms
XML-DA Gateway to OPC DA Server
via Internet access from client in USA to server in Europe
 
 1.2 s
 1.2 s
1.2 s

 


Notes:
1) OPCDA.NET clients create a group and add items only once and then call the read function repeatedly. XML-DA clients make independent read calls and the wrapper has to create a group and add items for each read call.
2) The large difference between read and poll times for XML-DA clients with XMLDA.NET is because a read connects to the OPC-DA server and reads the values from the server. For subscriptions the OPC-DA callback handler transfers the values into the XMLDA.NET subscription buffers and the poll only has to read the subscription buffer, no COM access is required.
3) The XML-DA server handles poll and read similarly and the processing time is mainly for the XML serialization respectively the Internet communication.

 

 


 

 

Express Interface (Xi / OPC .NET 3)

 

The Express Interface (Xi) specification was created in 2009 by a number of OPC vendor companies and end of 2009 the OPC Foundation adopted Xi as the OPC .NET 3.0 (WCF) specification.
In March 2010 the specification version 1.1 was released and the first products became available.
In October 2010 the specification version 1.20 was released.

The Express Interface (Xi) is a Microsoft .NET based interface designed for secure and reliable access to real-time and historical process automation system data. Xi provides a standard, .Net based interface for “classic” OPC server functionality, OPC Data Access (DA), OPC Alarms & Events (A&E) and OPC Historical Data Access (HDA) and represents a natural progression of Microsoft communication technology from Microsoft Component Object Model (COM) to .Net.

Xi provides the same functionality as the classic OPC servers while addressing some of the known shortcomings of classic OPC. The classic OPC servers are based on COM communications, which was state of the art when the OPC specifications
were created, but since the introduction of OPC DA in 1996, Microsoft has moved from COM to .Net communications. COM is efficient for local server access but can be difficult to configure for remote server access and problematic for communication through firewalls.
In addition to classic OPC functionality, Xi provides the following features:

  • Secure communications. Xi delivers a firewall friendly interface and patented security features to provide secure communications between process automation systems and higher level manufacturing execution systems (MES) and enterprise resources planning (ERP) systems.
  • Robust connectivity. Xi increases client connectivity robustness by maintaining the state of the client connection, allowing the
    client to reconnect quickly and easily if communications with the server were lost.
  • Plug and play. Xi provides automatic server discovery which allows Xi clients to automatically discover and connect to Xi servers.
  • One interface for real-time, historical and event data transfer. Xi provides a single interface to read and write real-time process data, subscribe to real-time alarms and events and read and write historical data.
  • Based on open, industry standards. Xi is based on Windows Communication Foundation (WCF), the latest communications technology available from Microsoft. Using WCF, a Xi server is able to offer industry standard communication protocols, such as the Transmission Control Protocol (TCP), the Hypertext Transfer Protocol (HTTP) and Secure Hypertext Transfer Protocol (HTTPS).
  • Easy to implement. Xi provides .Net client applications a simple .Net interface for easy access to classic OPC servers. Xi client applications can take advantage of new user interface technologies available in Windows Presentation Foundation (WPF).
  • Useable on all .NET platforms. .NET platforms such as Silverlight and the Compact Framework don't support DCOM but support s subset of WCF. Xi clients on these platforms can access classic OPC server through Xi converter servers.
  • Access data from anywhere. Xi delivers a secure and robust .Net interface that supports interprocess and TCP communications for .Net based Xi clients and a Web service interface for Internet based or non-Microsoft based Xi clients.
  • Future proof. As new WCF communication technologies become available, Xi can use these new technologies to provide additional connectivity options.
  • Easy migration from classic OPC. Xi products can wrap classic OPC clients and servers to provide a quick and easy migration path from OPC to Xi. Xi is
    also network compatible with classic OPC servers and thus may be used in the same system as classic OPC clients and servers.

Xi Products

Advosol offers a full range of Xi products for the software developer and the OPC system integrator.

Xi Converters
These servers convert between Xi and OPC DA, HDA, AE and XML DA and can be used by system integrators to make servers and clients for different OPC specifications interoperable. DCOM issues can be eliminated or minimized by using Xi for remote communication.
 DA server converting one Xi server
 Xi server converting DA/HDA/AE servers
 DA server converting Xi servers
 Xi server converting DA servers
 Xi server converting XML DA server



Xi Client Components
Advosol offers Xi components for all .NET platforms and Xi enhancement options for OPC DA products.
 Xi Option for OPCDA.NET
 PaXi Client Component for .NET3/4
 PaXi Client Component for .NETCF
 PaxiSL Client Component for Silverlight


Xi Server Toolkits
The Advosol Xi server toolkits provide the base for the development of specification compliant and interoperable Xi servers.
 XiPLUS (DA/HDA/AE)




 

 


 

OPC UA

OPC XML Webservices

Sub CategorySummary
XML DA Gateways

The OPC XML-DA Gateways offer a way to upgrade OPC solutions step-by-step to XML-DA web services. 

XML DA Developer Kits

Client development components and server toolkits help quickly develop .Net based XML-DA client and server applications.




Please select a subcategory above



Category Description

OPC Web Services

Web Services are currently the only high-level application-to-application communication technology embraced by virtually all platform providers including Microsoft, IBM, Sun, and Linux.
XML (eXtensible Markup Language) is one of the key enabling technologies for achieving global interconnectivity and it has industry-wide support as a standardized way of handling data among systems using a variety of operating systems. On a higher layer the SOAP specification defines remote procedure call messages in a platform independent fashion, using XML. Web services such as XML DA or UA base on SOAP and are defined in WSDL documents.

 

XML DA

In October 1999 the OPC Foundation announced that it will publish XML schema based on OPC specifications that define application interoperability and communications between disparate industrial automation devices, systems and applications running across the manufacturing enterprise.
In July 2003 the first version of the XML DA specification was released.
XML DA specifies a rather simple web service with eight methods that handle all of the features typically used in the OPC Data Access applications.

The XML DA specification didn't get the attention it deserves, mainly because the OPC Foundation announced the United Architecture specification shortly after the release of XML DA and allocated its resources on this new specification. Another reason is performance concerns. Due to the XML based communication XML DA is much slower than the COM based OPC DA. This caused users to decide for proprietary tunnel solutions instead of XML DA. However, it needs to be noted that XML DA is actually fast enough for many OPC data access applications.

XML DA Characteristics

  • Simple to implement
  • Limited functionality, Data Access only
  • Covers the requirements of most OPC Data Access applications
  • Can be used with web service extensions for secure communication
  • Much slower than COM based OPC
  • Products available

.NET3 (WCF) eliminates many of the web services short comings. The communication can now be configured for either high performance or security.

The XML DA specification defines SOAP messages for requests and responses. With .NET2 the communication is restricted the HTTP transport. With .NET3 (WCF) the communication can be configured in a wide range to include TCP and Pipe transports and many security options. The WCF basicHttp binding is compatible with .NET2.

 

 

OPC UA

In January 2004 the OPC Foundation tasked a work group to create the Unified Architecture (OPC UA) specification.

The OPC UA specification was to address the shortcomings of XML DA:

  • Integration of all OPC specification allowing alarms and historical data to be accessed in much the same way as current values.
  • A communication suitable on device and enterprise level.

These requirements made the OPC UA specification a daunting task and not all of the eleven parts of the OPC UA specification were released at end of 2006.
OPC UA is structured to have the required features for all OPC specifications (Data Access, Alarms&Events, Historical Data, Batch, Commands, Security) in it's base. Therefore the OPC UA base is complex and designed with a network database. A network database by itself is complicated. Due to the difficulty implementing and maintaining the network database model, the simpler relational databases are widely used instead.

To achieve the goal of OPC UA to be suitable on device and enterprise level OPC UA had to be defined for multiple communication implementations. OPC UA is therefore an 'inner' specification that can be accessed through different communications stacks (communication layer implementations) such as web services or a binary communication for high performance device level communication.

OPC UA server and clients not only need to be OPC UA compliant but also need to use a UA compliant communication stack.

 

The wide flexibility of UA allows servers to be structured in different ways. The UA client development tends to be complex because clients need to be able handle all UA allowed features.
So far UA is mainly used as a PLC interface. There are not yet many UA .NET applications.

 

 

OPC .NET 3 (Express Interface)

The Express Interface (Xi) specification was created in 2009 by a number of OPC vendor companies and end of 2009 the OPC Foundation adopted Xi as the OPC .NET 3.0 (WCF) specification.
In March 2010 the specification version 1.1 was released and the first products became available.
In October 2010 the specification version 1.20 was released.

 

Xi is a Microsoft .NET based interface designed for secure and reliable access to real-time and historical process automation system data. Xi provides a standard, .Net based interface for “classic” OPC server functionality, OPC Data Access (DA), OPC Alarms & Events (A&E) and OPC Historical Data Access (HDA) and represents a natural progression of Microsoft communication technology from Microsoft Component Object Model (COM) to .Net.

Xi provides the same functionality as the classic OPC servers while addressing some of the known shortcomings of classic OPC. The classic OPC servers are based on COM communications, which was state of the art when the OPC specifications were created, but since the introduction of OPC DA in 1996, Microsoft has moved from COM to .Net communications. COM is efficient for local server access but can be difficult to configure for remote server access and problematic for communication through firewalls.

Xi is designed for WCF and can use all current and future WCF communication and security features. Xi adds additional security features designed to combine high security with high performance.


Thanks to the simplicity there are already a number of Xi products on the market.

XML DA and Express Interface Comparison

OPC XML DAExpress Interface (Xi / OPC .NET 3.0)
Specification defines SOAP messages (WSDL). Can be implemented with .NET2 web services or WCF (.NET3)Specification defines WCF (.NET3.5) contracts.
OPC DA (Data Access) functionality only.
The specification is optimized for simplicity.
Combines DA, HDA and AE functionality into one interface.
The specification is designed for secure communication with high performance.
Subscriptions cannot be modified. This interface simplification can complicate the application development.Client access to data is managed in lists. These can be dynamically modified.
Specification is OPC copyright, available to OPC Foundation members only. Sample code is available to OPC Foundation members. The XML DA WSDL file is available to non-members.Specification and server base code is public domain. It can be downloaded from www.expressinterface.com.  The OPC Foundation provides client and server sample code to its members.
XML DA communication is state-less. There is no Connect/disconnect. Clients can e.g. use only the Read method.Clients need to establish a server context (with proper security) before data can be exchanged.
Clients can easily be created from WSDL with web services tools.Clients should be based on a Xi SDK for compliance reasons.
Secure communication is possible but not enforced.Secure communication is enforced and offers many options.
Only HTTP communication when implemented as .NET2 web service. WCF implementation can use all WCF communication options.All WCF communication options available on server and client machine can be used. For communication with non-Windows systems only basicHttp binding can be used.

 

 

Advosol XML DA Products
Advosol was first to deliver software components for XML-DA clients and servers and now offers matured software in version 5. Version 1 was based on the OPC XML-DA pre-release specificationa and allowed users and us to create advanced solutions and build up know-how. Version 2 was released shortly after the XML-DA standard V1.0 was available. It was tested at the Spring 2004 OPC Interoperabiliy workshop with all available XML-DA products. Version 3 offers enhanced performance, functionality and ease of use. Version 4 uses.NET Framework 2.0. Version 5 supports Windows Vista .NET3 (WCF) and allows the communication to be configured for either high performance through TCP or Named Pipe transports or for high security with X.509 certificate based authentication and/or encryption.
The Advosol software products are compliance tested with the OPC Foundation test tools.

Advosol offers software development tools for XML-DA clients, XML-DA Servers and Gateways that provide a sound base for new applications and an easy migration path for the thousands of OPC DA products in use today.

XML-DA server-side GatewayThe XDAGW-SS gateway enables OPC-DA servers to be accessed from XML-DA clients. Using the gateway is the quickest way to make an existing OPC DA server accessible from a remote location.
XDAGW-SS can be configured to restrict access to a item subset or allow only read access.
XML-DA client-side Gateway

The XDAGW-CS gateway allows OPC DA clients to access XML-DA servers. Only minimal configuration is required. XDAGW-CS is OPC DA V2.05 and V3 compliance tested.

The XML-DA Bridge consists of a pair of gateways, the XDAGW-SS gateway and the XDAGW-CS gateway.
Existing OPC DA clients can access OPC DA servers over the Internet.

OPC Exchange ServerThe Exchange Server aggregates data from multiple OPC DA servers and exchanges data between these servers.
Accessed as an XML DA server the Exchange Server acts as a gateway web service to multiple OPC DA servers.

XML-DA Client ComponentThe XMLDA.NET client component allows XML-DA clients to access local OPC DA V2 server directly, without going through XML serialization, offering highly improved performance.
Clients can be developed as state of the art web services clients even if OPC DA COM server need to be accessed.

XML-DA Server ToolkitGateways can be used to wrap OPC DA servers to XML-DA, but a native XML-DA server offers higher performance and better configuration options.
The XDASrv Server Toolkit makes the development of native XML-DA servers simple an quick. The generic XML-DA server is provided as a .Net web service. The user only has to develop a .Net assembly with a few item configuration and device access methods. Optional methods can be implemented to optimize performance and realize demanding applications.
Advosol - OPCDA.NET, OPC HDA .NET, DA server converting one Xi server, OPC DA Server-Side XML Gateway Hong Kong/Asia Distributor, Reseller

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