dOPC and UA

With version 5.0 dOPC now supports also OPC UA (Unified Architecture). We have implemented the fastest OPC UA protocol which is OPC UA Binary (opc.tcp://...). This protocol must be supported on any OPC UA server. For further information about OPC UA please take a further look at this Wiki. For the OPC UA specifications (specially Part 4: Services) please click here.

As dOPC developer you can easily change to OPC UA. Just precede the server name with "opc.tcp://..." to instruct dOPC to use UA connections. Apart from that the handling is the same as with a 'classic' or XML DA OPC server.

The dOPC Client Toolkit supports OPC UA in 2 ways:

1. TdOPCDAClient

With the TdOPCDAClient it is possible to develop Data Access Client (DA) not only for UA. The TdOPCDAClient is also compatible with OPC COM (Classic) and OPC XML DA. You just have to enter the connection string (Property: ServerName) to change from one server type to a other. Our dOPC Explorer is a good example it. The dOPC Explorer is complete written with the help of the TdOPCDAClient and the TdOPCServerBrowser component. Here is an example how you can connect to an OPC UA server:

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uses
 dOPCDA;

procedure OPCUAConnect(OPCClient : TdOPCUAClient);
begin
 OPCClient.ServerName := 'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
 OPCClient.Active := true;
 ShowMessage('Connected to server');
end;

2. TdOPCUAClient

For the start point to develop OPC UA clients it is recommended to use the TdOPCDAClient component, because it uses the TdOPCUAClient component internally, but it is much easier to handle.

However, with the TdOPCUAClient it is possible to connect to any OPC UA Server via the binary protocol (opc.tcp://...). The usage of the our UA component is very easy. All connecting and disconnecting activities are done in the component. But please note: With this component it is not possible to connect to other OPC server like OPC Classic COM server or OPC XML DA server.

Here is an example how you can connect to an OPC UA server:

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uses
 ua.client;

procedure OPCUAConnect(OPCClient : TdOPCUAClient);
begin
 OPCClient.URL := 'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer';
 OPCClient.Active := true;
 ShowMessage('Connected to server');
end;

The TdOPCUAClient supports all OPC UA Service calls which are in detailed descript in the OPC UA Specification (Part 4: Services) You can download the specification at: https://www.opcfoundation.org or you will find the OPC UA specification online at: https://reference.opcfoundation.org

It is recommended to read the OPC UA Specification Part 4 first.

Below you will find an example how you can make an service call with the TdOPCUAClient component.

The example shows you how to call the GetEndpoints service. For further information about this service, please look at: OPC UA Specification Part 4 Discovery Service Set "GetEndpoints".

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uses
 ua.datatypes;

procedure CallGetEndpoints(UAClient: TdOPCUAClient; Info: TStrings);
var
 S: uaGetEndpoints;
 Endpoint: uaEndpointDescription;
begin
 S := uaGetEndpoints.Create(UAClient);
 try
   S.Request.EndpointUrl := UAClient.Url;
   S.Run;
   for Endpoint in S.Response.Endpoints do
     Info.Add('+ '+Endpoint.EndpointUrl);
 finally
   S.Free;
 end;
end;

You can call all other OPC UA service calls in the same way.

Here is an template how to use:

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var
 ServiceCall: ua<NameOfServiceCall> // NameOfServiceCall = Service descripted in Part 4
begin
 ServiceCall := ua<NameOfServiceCall>.Create(<TdOPCUAClientObject>)
 try
   ServiceCall.Request.<InputParam> := <InputParamValue>
   ServiceCall.Run;
   ServiceCall.Response.<OutputParam>
 finally
   ServiceCall.Free;
 end;
end;

Below you will find all OPC UA Service calls ua<NameOfServiceCall> which are supported by the dOPC Client Toolkit and in detail descript in the OPC UA Specification Part 4 Services. In the unit ua.datatypes and ua.buildintypes you will find nearly all needed objects.

OPC UA Service call	Description
ua FindServers	Finds the servers known to the discovery server.
ua FindServersOnNetwork	Returns the servers known to a Discovery Server
ua GetEndpoints	Gets the endpoints used by the server.
ua RegisterServer	Registers a server with the discovery server.
ua RegisterServer2	Is implemented by Discovery Servers
ua OpenSecureChannel	Creates a secure channel with a server.
ua CloseSecureChannel	Closes a secure channel.
ua CreateSession	Creates a new session with the server.
ua ActivateSession	Activates a session with the server.
ua CloseSession	Closes a session with the server.
ua Cancel	Cancels an outstanding request.
ua AddNodes	Adds one or more nodes to the server address space.
ua AddReferences	Adds one or more references to the server address space.
ua DeleteNodes	Delete one or more nodes from the server address space.
ua DeleteReferences	Delete one or more references from the server address space.
ua Browse	Browse the references for one or more nodes from the server address space.
ua BrowseNext	Continues one or more browse operations.
ua TranslateBrowsePathsToNodeIds	Translates one or more paths in the server address space.
ua RegisterNodes	Registers one or more nodes for repeated use within a session.
ua UnregisterNodes	Unregisters one or more previously registered nodes.
ua QueryFirst	This service is used to issue a Query request to the Server
ua QueryNext	look at OPC UA Spec Part 4 Services
ua Read	Is used to read one or more attributes or nodes.
ua HistoryRead	look at OPC UA Spec Part 4 Services
ua Write	Is used to write values to one or more attributes or nodes
ua HistoryUpdate	look at OPC UA Spec Part 4 Services
ua Call	Is used to call a list of methods
ua CreateMonitoredItems	look at OPC UA Spec Part 4 Services
ua ModifyMonitoredItems	look at OPC UA Spec Part 4 Services
ua SetMonitoringMode	look at OPC UA Spec Part 4 Services
ua SetTriggering	look at OPC UA Spec Part 4 Services
ua DeleteMonitoredItems	look at OPC UA Spec Part 4 Services
ua ModifySubscription	look at OPC UA Spec Part 4 Services
ua SetPublishingMode	look at OPC UA Spec Part 4 Services
ua Publish	look at OPC UA Spec Part 4 Services
ua Republish	look at OPC UA Spec Part 4 Services
ua TransferSubscriptions	look at OPC UA Spec Part 4 Services
ua DeleteSubscriptions	look at OPC UA Spec Part 4 Services
ua CreateSubscription	look at OPC UA Spec Part 4 Services

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