OPC Studio User's Guide and Reference
OPC UA Global Discovery Client
Client and Subscriber Development > Features > Specialized Client Objects > OPC UA Global Discovery Client
In This Topic

The OPC UA Global Discovery Client is a specialized OPC UA client object for global discovery. In the OPC UA specifications, the functionality covered by this type is described in Part 12: Discovery and Global Services, in the Global Discovery Server section.

This specialized client object can be derived from IEasyUAClient Interface using the AsGlobalDiscoveryClient Extension Method, or it can be created standalone as EasyUAGlobalDiscoveryClient Component.

This interface contains methods to communicate with the OPC UA Global Discovery Server (GDS) using its information model for global discovery, making the work of assembling the proper OPC UA method parameters and retrieving the results. The methods allow querying for applications and/or servers, and registering, unregistering or updating application registrations in the GDS. Only the global discovery aspect of the GDS information is covered by this interface. Certificate management (CM), key credential management, and authorization services are treated separately.

Before deciding to use methods provided by this specialized client, it is recommended that you have a look at the IEasyUAClientServerApplication service (see OPC UA Client-Server Application Service), available from IServiceProvider.GetService method from the IEasyUAClient interface. The client application service works on higher level, and conveniently combines several methods together to achieve the typically needed functionality related to GDS and certificate management in OPC UA.

Available methods are:

The features discussed here, or some of them, may not be available in all editions of the product. Check the Product Editions page for differences between the editions. The trial license has all features enabled (and is limited in period for which it provides valid data), but licenses for specific commercial editions may have functionality limitations.

Example

.NET

// Shows how to check if an application needs to update its certificate.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.AddressSpace;
using OpcLabs.EasyOpc.UA.Application;
using OpcLabs.EasyOpc.UA.Extensions;
using OpcLabs.EasyOpc.UA.Gds;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.Gds._EasyUACertificateManagementClient
{
    class GetCertificateStatus
    {
        public static void Main1()
        {
            // Define which GDS we will work with.
            UAEndpointDescriptor gdsEndpointDescriptor = 
                ((UAEndpointDescriptor)"opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer")
                .WithUserNameIdentity("appadmin", "demo");

            // Register our client application with the GDS, so that we obtain an application ID that we need later.
            // Obtain the application interface.
            EasyUAApplication application = EasyUAApplication.Instance;
            UANodeId applicationId;
            try
            {
                applicationId = application.RegisterToGds(gdsEndpointDescriptor);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }
            Console.WriteLine("Application ID: {0}", applicationId);

            // Instantiate the certificate management client object
            var certificateManagementClient = new EasyUACertificateManagementClient();

            // Check if the application needs to update its certificate.
            bool updateRequired;
            try
            {
                updateRequired = certificateManagementClient.GetCertificateStatus(gdsEndpointDescriptor, applicationId,
                    UANodeId.Null, UANodeId.Null);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Display results
            Console.WriteLine("Update required: {0}", updateRequired);
        }


        // Example output:
        //Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61
        //Update required: False
    }
}

# Shows how to check if an application needs to update its certificate.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in Python on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-Python .
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.AddressSpace import *
from OpcLabs.EasyOpc.UA.Application import *
from OpcLabs.EasyOpc.UA.Extensions import *
from OpcLabs.EasyOpc.UA.Gds import *
from OpcLabs.EasyOpc.UA.OperationModel import *


# Define which GDS we will work with.
gdsEndpointDescriptor = UAEndpointDescriptor('opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer')
gdsEndpointDescriptor = UAEndpointDescriptorExtension.WithUserNameIdentity(gdsEndpointDescriptor,
                                                                           'appadmin', 'demo')

# Register our client application with the GDS, so that we obtain an application ID that we need later.
# Obtain the application interface.
application = EasyUAApplication.Instance
try:
    print('Registering to GDS...')
    applicationId = application.RegisterToGds(gdsEndpointDescriptor)
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()
print('Application ID: ', applicationId, sep='')

# Instantiate the certificate management client object.
certificateManagementClient = EasyUACertificateManagementClient()

# Check if the application needs to update its certificate.
try:
    updateRequired = certificateManagementClient.GetCertificateStatus(gdsEndpointDescriptor,
                                                                      applicationId,
                                                                      UANodeId.Null,    # certificateGroupId
                                                                      UANodeId.Null)    # certificateTypeId
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
print('Update required: ', updateRequired, sep='')

print()
print('Finished.')

' Shows how to check if an application needs to update its certificate.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports Microsoft.Extensions.DependencyInjection
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.AddressSpace
Imports OpcLabs.EasyOpc.UA.Application
Imports OpcLabs.EasyOpc.UA.Application.ComTypes
Imports OpcLabs.EasyOpc.UA.Extensions
Imports OpcLabs.EasyOpc.UA.Gds
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace Gds._EasyUACertificateManagementClient
    Friend Class GetCertificateStatus
        Public Shared Sub Main1()

            ' Define which GDS we will work with.
            Dim gdsEndpointDescriptor As UAEndpointDescriptor =
                New UAEndpointDescriptor("opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer") _
                .WithUserNameIdentity("appadmin", "demo")

            ' Register our client application with the GDS, so that we obtain an application ID that we need later.
            ' Obtain the application interface.
            Dim application = EasyUAApplication.Instance

            ' Create an application registration in the GDS, assigning it a new application ID.
            Dim applicationId As UANodeId
            Try
                applicationId = application.RegisterToGds(gdsEndpointDescriptor)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Instantiate the certificate management client object
            Dim certificateManagementClient = New EasyUACertificateManagementClient()

            ' Check if the application needs to update its certificate.
            Dim updateRequired As Boolean
            Try
                updateRequired = certificateManagementClient.GetCertificateStatus(gdsEndpointDescriptor, applicationId,
                    UANodeId.Null, UANodeId.Null)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display results
            Console.WriteLine("Update required: {0}", updateRequired)
        End Sub
    End Class
End Namespace

COM

// Shows how to check if an application needs to update its certificate.
//
// Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

class procedure GetCertificateStatus.Main;
var
  Application: TEasyUAApplication;
  ApplicationId: _UANodeId;
  CertificateManagementClient: OpcLabs_EasyOpcUA_TLB._EasyUACertificateManagementClient;
  GdsEndpointDescriptor: _UAEndpointDescriptor;
  NullNodeId: _UANodeId;
  UpdateRequired: boolean;
begin
  // Define which GDS we will work with.
  GdsEndpointDescriptor := CoUAEndpointDescriptor.Create;
  GdsEndpointDescriptor.UrlString := 'opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer';
  GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.UserName := 'appadmin';
  GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.Password := 'demo';

  // Register our client application with the GDS, so that we obtain an application ID that we need later.
  // Obtain the application interface.
  Application := TEasyUAApplication.Create(nil);

  // Create an application registration in the GDS, assigning it a new application ID.
  try
    ApplicationId := Application.RegisterToGds(GdsEndpointDescriptor);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
    end;
  end;

  WriteLn('Application ID: ', ApplicationId.ToString);

  // Instantiate the certificate management client object
  CertificateManagementClient := CoEasyUACertificateManagementClient.Create;

  // Check if the application needs to update its certificate.
  NullNodeId := CoUANodeId.Create;
  UpdateRequired := false;
  try
    UpdateRequired := CertificateManagementClient.GetCertificateStatus(GdsEndpointDescriptor, ApplicationId, NullNodeId, NullNodeId);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
    end;
  end;

  // Display results
  WriteLn('Update required: ', UpdateRequired);

  // Example output:
  //Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61
  //Update required: FALSE

end;

REM Shows how to check if an application needs to update its certificate.
REM
REM Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Private Sub EasyUACertificateManagementClient_GetCertificateStatus_Main_Command_Click()
    OutputText = ""
        
    ' Define which GDS we will work with.
    Dim gdsEndpointDescriptor As New UAEndpointDescriptor
    gdsEndpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer"
    gdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.UserName = "appadmin"
    gdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.Password = "demo"
    
    ' Register our client application with the GDS, so that we obtain an application ID that we need later.
    ' Obtain the application interface
    Dim Application As New EasyUAApplication
    
    ' Create an application registration in the GDS, assigning it a new application ID.
    On Error Resume Next
    Dim applicationId As UANodeId
    Set applicationId = Application.RegisterToGds(gdsEndpointDescriptor)
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    OutputText = OutputText & "Application ID: " & applicationId & vbCrLf

    ' Instantiate the certificate management client object
    Dim certificateManagementClient As New EasyUACertificateManagementClient
    
    ' Check if the application needs to update its certificate.
    Dim nullNodeId As New UANodeId
    Dim updateRequired As Boolean: updateRequired = False
    On Error Resume Next
    updateRequired = certificateManagementClient.GetCertificateStatus(gdsEndpointDescriptor, applicationId, nullNodeId, nullNodeId)
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    ' Display results
    OutputText = OutputText & "Update required: " & updateRequired & vbCrLf

    ' Example output:
    'Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61
    'Update required: FALSE
End Sub

Rem Shows how to check if an application needs to update its certificate.
Rem
Rem Find all latest examples here : https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Option Explicit

' Define which GDS we will work with.
Dim GdsEndpointDescriptor: Set GdsEndpointDescriptor = CreateObject("OpcLabs.EasyOpc.UA.UAEndpointDescriptor")
GdsEndpointDescriptor.UrlString = "opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer"
GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.UserName = "appadmin"
GdsEndpointDescriptor.UserIdentity.UserNameTokenInfo.Password = "demo"

' Register our client application with the GDS, so that we obtain an application ID that we need later.
' Obtain the application interface.
Dim Application: Set Application = CreateObject("OpcLabs.EasyOpc.UA.Application.EasyUAApplication")
On Error Resume Next
Dim ApplicationId: Set ApplicationId = Application.RegisterToGds(GdsEndpointDescriptor)
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0
WScript.Echo "Application ID: " & ApplicationId

' Instantiate the certificate management client object
Dim CertificateManagementClient: Set CertificateManagementClient = _
    CreateObject("OpcLabs.EasyOpc.UA.Gds.EasyUACertificateManagementClient")

' Check if the application needs to update its certificate.
Dim NullNodeId: Set NullNodeId = CreateObject("OpcLabs.EasyOpc.UA.AddressSpace.UANodeId")
On Error Resume Next
Dim UpdateRequired: UpdateRequired = CertificateManagementClient.GetCertificateStatus( _
    GdsEndpointDescriptor, ApplicationId, NullNodeId, NullNodeId)
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

' Display results
WScript.Echo "Update required: " & UpdateRequired


' Example output:
'Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61
'Update required: False
See Also
Specialized Client Objects
Features
OPC UA Certificate Management Client

Examples - OPC UA GDS and CM

Examples - OPC UA GDS and CM - Find all registrations
Examples - OPC UA GDS and CM - Query for applications
Examples - OPC UA GDS and CM - Query for servers
Examples - OPC UA GDS and CM - Unregister all clients
Examples - OPC UA GDS and CM - Browse certificate groups

Recommended

OPC UA Client-Server Application Service

 

 

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