FindApplications Method (_EasyUAGlobalDiscoveryClient)

Finds the application records for an OPC UA application known to the GDS.

Syntax

[NotNull()]
object[] FindApplications( 
   object gdsEndpointDescriptor,
   string applicationUriString
)

[NotNull()]
array<Object^>^ FindApplications( 
   Object^ gdsEndpointDescriptor,
   String^ applicationUriString
)

'Declaration
 
<NotNullAttribute()>
Function FindApplications( _
   ByVal gdsEndpointDescriptor As Object, _
   ByVal applicationUriString As String _
) As Object()

'Usage
 
Dim instance As _EasyUAGlobalDiscoveryClient
Dim gdsEndpointDescriptor As Object
Dim applicationUriString As String
Dim value() As Object
 
value = instance.FindApplications(gdsEndpointDescriptor, applicationUriString)

Parameters

gdsEndpointDescriptor

Endpoint descriptor. Identifies the OPC-UA server. The server must be a Global Directory Server (GDS).

Because the OpcLabs.EasyOpc.UA.UAEndpointDescriptor has implicit conversions from System.String and System.Uri, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a string (representing the endpoint URL, or a so-called OPC UA endpoint descriptor string), or a System.Uri object, in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can use the OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromString or OpcLabs.EasyOpc.UA.UAEndpointDescriptor.FromUri static method instead.

Also, because the OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement and OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement have an implicit conversion to OpcLabs.EasyOpc.UA.UAEndpointDescriptor, in languages that support implicit conversion operators (such as C# or VB.NET), you can simply use a OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement (results from OPC UA discovery) in place of this parameter, and the corresponding endpoint descriptor will be constructed automatically. When the implicit conversion operators are not supported (such as with Python.NET), you can convert a (non-null) OpcLabs.EasyOpc.UA.Discovery.UAApplicationElement or OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement to OpcLabs.EasyOpc.UA.UAEndpointDescriptor using the ToUAEndpointDescriptor or ToUAEndpointDescriptor method instead.

If you are using OPC Wizard (for server development), an implicit conversion from OpcLabs.EasyOpc.UA.EasyUAServerCore can be used in the same way to simply pass the server object in place of this parameter, which will use its OpcLabs.EasyOpc.UA.EasyUAServerCore.EffectiveServerDescriptor property for the connection.

The value of this parameter cannot be null (Nothing in Visual Basic).

applicationUriString

The application URI that identifies the application of interest.

The value of this parameter can be null (Nothing in Visual Basic).

Return Value

A list of application records that match the application URI given by .

This method never returns null (Nothing in Visual Basic).

The individual elements of the returned value are never null (Nothing in Visual Basic).

Exceptions

Exception Description

Exception	Description
System.ArgumentNullException	A `null` reference (`Nothing` in Visual Basic) is passed to a method that does not accept it as a valid argument. This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.
OpcLabs.EasyOpc.UA.OperationModel.UAException	The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause. This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

System.ArgumentNullException

A null reference (Nothing in Visual Basic) is passed to a method that does not accept it as a valid argument.

This is a usage error, i.e. it will never occur (the exception will not be thrown) in a correctly written program. Your code should not catch this exception.

OpcLabs.EasyOpc.UA.OperationModel.UAException

The OPC UA operation has failed. This operation exception in uniformly used to allow common handling of various kinds of errors. The System.Exception.InnerException always contains information about the actual error cause.

This is an operation error that depends on factors external to your program, and thus cannot be always avoided. Your code must handle it appropriately.

Remarks

If the returned array has zero length then the GDS does not have an entry for the application URI given by applicationUriString.

"FindApplications is used to find the ApplicationId for an OPC UA Application known to the GDS. In normal situations the list of records returned will not have more than one entry, however, system configuration errors can create situations where the GDS has multiple entries for a single ApplicationUri. If this happens a human will likely have to look at records to determine which record is the true match for the ApplicationUri."

If you want to find the registration information for the current client application, it is recommended that you use the higher-level OpcLabs.EasyOpc.UA.Application.IEasyUAClientServerApplication.FindGdsRegistrations method instead.

This member or type is for use from COM. It is not meant to be used from .NET or Python. Refer to the corresponding .NET member or type instead, if you are developing in .NET or Python.

Example

// Shows how to find all registrations in the GDS.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in C# on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-CSharp .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.Discovery;
using OpcLabs.EasyOpc.UA.Extensions;
using OpcLabs.EasyOpc.UA.Gds;
using OpcLabs.EasyOpc.UA.OperationModel;

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

            // Instantiate the global discovery client object
            var globalDiscoveryClient = new EasyUAGlobalDiscoveryClient();

            // Find all (client or server) applications registered in the GDS.
            UAApplicationDescription[] applicationDescriptionArray;
            try
            {
                globalDiscoveryClient.QueryApplications(
                    gdsEndpointDescriptor: gdsEndpointDescriptor,
                    startingRecordId: 0,
                    maximumRecordsToReturn: 0,
                    applicationName: "",
                    applicationUriString: "",
                    applicationTypes: UAApplicationTypes.All,
                    productUriString: "",
                    serverCapabilities: new string[0],
                    lastCounterResetTime: out _,
                    nextRecordId: out _,
                    applications: out applicationDescriptionArray);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // For each application returned by the query, find its registrations in the GDS.
            foreach (UAApplicationDescription applicationDescription in applicationDescriptionArray)
            {
                Console.WriteLine();
                Console.WriteLine("Application URI string: {0}", applicationDescription.ApplicationUriString);

                UAApplicationRecordDataType[] applicationRecordArray;
                try
                {
                    applicationRecordArray = globalDiscoveryClient.FindApplications(
                        gdsEndpointDescriptor,
                        applicationDescription.ApplicationUriString);
                }
                catch (UAException uaException)
                {
                    Console.WriteLine("  *** Failure: {0}", uaException.GetBaseException().Message);
                    continue;
                }

                // Display results
                foreach (UAApplicationRecordDataType applicationRecord in applicationRecordArray)
                    Console.WriteLine("  Application ID: {0}", applicationRecord.ApplicationId);
            }


            // Example output:
            //
            //Application URI string: urn:sampleserver
            //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=09ecaa08-6ec6-462c-a214-1e66a3099107
            //
            //Application URI string: urn:alarmconditionserver
            //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=783e1e9a-8036-43b6-928f-97488c460266
            //
            //Application URI string: urn:PC:MultiTargetUADocExamples:5.54.1026.1:neutral:null
            //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=9e700ea5-55a6-4c3c-ba9f-b91c890dc519
            //
            //Application URI string: urn:PC:UADocExamples:5.56.0.16:neutral:null
            //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=e182e28c-086b-4fc7-82c7-70ca7cda3033
            //
            //Application URI string: urn:PC:cscript:5.812.10240.16384
            //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61
        }
    }
}

' Shows how to find all registrations in the GDS.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
' OPC client and subscriber examples in VB.NET on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBNET .
' Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
' a commercial license in order to use Online Forums, and we reply to every post.

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.Discovery
Imports OpcLabs.EasyOpc.UA.Extensions
Imports OpcLabs.EasyOpc.UA.Gds
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace Gds._EasyUAGlobalDiscoveryClient
    Friend Class FindApplications
        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("appuser", "demo")

            ' Instantiate the global discovery client object
            Dim globalDiscoveryClient = New EasyUAGlobalDiscoveryClient()

            ' Find all (client or server) applications registered in the GDS.
            Dim applicationDescriptionArray() As UAApplicationDescription = Nothing
            Try
                Dim lastCounterResetTime As DateTime
                Dim nextRecordId As Long
                globalDiscoveryClient.QueryApplications(
                    gdsEndpointDescriptor:=gdsEndpointDescriptor,
                    startingRecordId:=0,
                    maximumRecordsToReturn:=0,
                    applicationName:="",
                    applicationUriString:="",
                    applicationTypes:=UAApplicationTypes.All,
                    productUriString:="",
                    serverCapabilities:=New String() {},
                    lastCounterResetTime:=lastCounterResetTime,
                    nextRecordId:=nextRecordId,
                    applications:=applicationDescriptionArray)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' For each application returned by the query, find its registrations in the GDS.
            For Each applicationDescription As UAApplicationDescription In applicationDescriptionArray
                Console.WriteLine()
                Console.WriteLine("Application URI string: {0}", applicationDescription.ApplicationUriString)

                Dim applicationRecordArray() As UAApplicationRecordDataType
                Try
                    applicationRecordArray = globalDiscoveryClient.FindApplications(
                        gdsEndpointDescriptor,
                        applicationDescription.ApplicationUriString)
                Catch uaException As UAException
                    Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                    Continue For
                End Try

                ' Display results
                For Each applicationRecord As UAApplicationRecordDataType In applicationRecordArray
                    Console.WriteLine("  Application ID: {0}", applicationRecord.ApplicationId)
                Next applicationRecord
            Next applicationDescription
        End Sub
    End Class
End Namespace

// Shows how to find all registrations in the GDS.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
// OPC client and subscriber examples in Object Pascal (Delphi) on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-OP .
// Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
// a commercial license in order to use Online Forums, and we reply to every post.

class procedure FindApplications.Main;
var
  ApplicationDescription: _UAApplicationDescription;
  ApplicationDescriptionArray: OleVariant;
  ApplicationName: WideString;
  ApplicationRecord: _UAApplicationRecordDataType;
  ApplicationRecordArray: OleVariant;
  ApplicationUriString: WideString;
  GlobalDiscoveryClient: OpcLabs_EasyOpcUA_TLB._EasyUAGlobalDiscoveryClient;
  GdsEndpointDescriptor: _UAEndpointDescriptor;
  I, J: integer;
  LastCounterResetTime: TDateTime;
  MaximumRecordsToReturn: Integer;
  NextRecordId: Integer;
  ProductUriString: WideString;
  ServerCapabilities: array of string;
  StartingRecordId: Integer;
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';

  // Instantiate the global discovery client object
  GlobalDiscoveryClient := CoEasyUAGlobalDiscoveryClient.Create;

  // Find all (client or server) applications registered in the GDS.
  StartingRecordId := 0;
  MaximumRecordsToReturn := 0;
  ApplicationName := '';
  ApplicationUriString := '';
  ProductUriString := '';
  try
    GlobalDiscoveryClient.QueryApplications(
      GdsEndpointDescriptor,
      StartingRecordId,
      MaximumRecordsToReturn,
      ApplicationName,
      ApplicationUriString,
      UAApplicationTypes_All,
      ProductUriString,
      ServerCapabilities,
      LastCounterResetTime,
      NextRecordId,
      ApplicationDescriptionArray);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
    end;
  end;

  // For each application returned by the query, find its registrations in the GDS.
  for I := VarArrayLowBound(ApplicationDescriptionArray,1) to VarArrayHighBound(ApplicationDescriptionArray,1) do
  begin
    ApplicationDescription := IUnknown(ApplicationDescriptionArray[I]) as _UAApplicationDescription;
    WriteLn;
    WriteLn('Application URI string: ', ApplicationDescription.ApplicationUriString);
    try
    TVarData(ApplicationRecordArray).VType := varArray or varVariant;
    TVarData(ApplicationRecordArray).VArray := PVarArray(
      GlobalDiscoveryClient.FindApplications(
        GdsEndpointDescriptor,
        ApplicationDescription.ApplicationUriString));
    except
      on E: EOleException do
      begin
        WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
        Continue;
      end;
    end;
      for J := VarArrayLowBound(ApplicationRecordArray, 1) to VarArrayHighBound(ApplicationRecordArray, 1) do
      begin
        // Display results
        ApplicationRecord := IUnknown(ApplicationRecordArray[J]) as _UAApplicationRecordDataType;
        WriteLn('  Application ID: ', ApplicationRecord.ApplicationId.ToString);
      end;
  end;

  // Example output:
  //
  //Application URI string: urn:sampleserver
  //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=09ecaa08-6ec6-462c-a214-1e66a3099107
  //
  //Application URI string: urn:alarmconditionserver
  //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=783e1e9a-8036-43b6-928f-97488c460266
  //
  //Application URI string: urn:PC:MultiTargetUADocExamples:5.54.1026.1:neutral:null
  //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=9e700ea5-55a6-4c3c-ba9f-b91c890dc519
  //
  //Application URI string: urn:PC:UADocExamples:5.56.0.16:neutral:null
  //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=e182e28c-086b-4fc7-82c7-70ca7cda3033
  //
  //Application URI string: urn:PC:cscript:5.812.10240.16384
  //  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61

end;

Rem Shows how to find all registrations in the GDS.
Rem
Rem Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
Rem OPC client and subscriber examples in VBScript on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VBScript .
Rem Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
Rem a commercial license in order to use Online Forums, and we reply to every post.

Option Explicit

Const UAApplicationTypes_All = 7

' 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"

' Instantiate the global discovery client object
Dim GlobalDiscoveryClient: Set GlobalDiscoveryClient = CreateObject("OpcLabs.EasyOpc.UA.Gds.EasyUAGlobalDiscoveryClient")

' Find all (client or server) applications registered in the GDS.
Dim startingRecordId: startingRecordId = 0
Dim maximumRecordsToReturn: maximumRecordsToReturn = 0
Dim applicationName: applicationName = ""
Dim applicationUriString: applicationUriString = ""
Dim productUriString: productUriString = ""
Dim serverCapabilities: serverCapabilities = Array()
Dim lastCounterResetTime
Dim nextRecordId
Dim applicationDescriptionArray
On Error Resume Next
GlobalDiscoveryClient.QueryApplications _
    GdsEndpointDescriptor, _
    startingRecordId, _
    maximumRecordsToReturn, _
    applicationName, _
    applicationUriString, _
    UAApplicationTypes_All, _
    productUriString, _
    serverCapabilities, _ 
    lastCounterResetTime, _
    nextRecordId, _
    applicationDescriptionArray
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

' For each application returned by the query, find its registrations in the GDS.
Dim ApplicationDescription
For Each ApplicationDescription In applicationDescriptionArray
    WScript.Echo
    WScript.Echo "Application URI string: " & ApplicationDescription.ApplicationUriString

    On Error Resume Next
    Dim applicationRecordArray: applicationRecordArray = GlobalDiscoveryClient.FindApplications( _
        gdsEndpointDescriptor, _
        ApplicationDescription.ApplicationUriString)
    If Err.Number <> 0 Then
        WScript.Echo "  *** Failure: " & Err.Source & ": " & Err.Description
    Else
        Dim ApplicationRecord
        For Each ApplicationRecord In applicationRecordArray
            ' Display results
            WScript.Echo "  Application ID: " & ApplicationRecord.ApplicationId
        Next
    End If
    On Error Goto 0
Next


' Example output:
'
'Application URI string: urn:sampleserver
'  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=09ecaa08-6ec6-462c-a214-1e66a3099107
'
'Application URI string: urn:alarmconditionserver
'  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=783e1e9a-8036-43b6-928f-97488c460266
'
'Application URI string: urn:PC:MultiTargetUADocExamples:5.54.1026.1:neutral:null
'  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=9e700ea5-55a6-4c3c-ba9f-b91c890dc519
'
'Application URI string: urn:PC:UADocExamples:5.56.0.16:neutral:null
'  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=e182e28c-086b-4fc7-82c7-70ca7cda3033
'
'Application URI string: urn:PC:cscript:5.812.10240.16384
'  Application ID: nsu=http://opcfoundation.org/UA/GDS/applications/ ;ns=2;g=aec94459-f513-4979-8619-8383555fca61

# Shows how to find all registrations in the GDS.
#
# 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 .
# Missing some example? Ask us for it on our Online Forums, https://www.opclabs.com/forum/index ! You do not have to own
# a commercial license in order to use Online Forums, and we reply to every post.
# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from System import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.Discovery 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')

# Instantiate the global discovery client object.
globalDiscoveryClient = EasyUAGlobalDiscoveryClient()

# Find all (client or server) applications registered in the GDS.
try:
    _, _, _, applicationDescriptionArray = globalDiscoveryClient.QueryApplications(
        gdsEndpointDescriptor,
        0,  # startingRecordId
        0,  # maximumRecordsToReturn
        '', # applicationName
        '', # applicationUriString
        UAApplicationTypes.All, # applicationTypes
        '', # productUriString
        Array.Empty[String](),  # serverCapabilities
        DateTime(), # out lastCounterResetTime
        0,  # out nextRecordId
        Array.Empty[UAApplicationDescription]()) # out applications
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# For each application returned by the query, find its registrations in the GDS.
for applicationDescription in applicationDescriptionArray:
    print()
    print('Application URI string: ', applicationDescription.ApplicationUriString, sep='')

    try:
        applicationRecordArray = globalDiscoveryClient.FindApplications(
            gdsEndpointDescriptor,
            applicationDescription.ApplicationUriString)
    except UAException as uaException:
        print('  *** Failure: ' + uaException.GetBaseException().Message)
        continue

    # Display results.
    for applicationRecord in applicationRecordArray:
        print('  Application ID: ', applicationRecord.ApplicationId, sep='')

print()
print('Finished.')

Requirements

Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows

Reference

_EasyUAGlobalDiscoveryClient Interface
_EasyUAGlobalDiscoveryClient Members

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