Examples - OPC UA GDS and CM - Query for servers

.NET

C#
VB.NET

// Shows how to find server applications that meet the specified filters, using the global discovery client.
//
// 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.Discovery;
using OpcLabs.EasyOpc.UA.Gds;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples.Gds._EasyUAGlobalDiscoveryClient
{
    class QueryServers
    {
        public static void Main1()
        {
            // Instantiate the global discovery client object
            var globalDiscoveryClient = new EasyUAGlobalDiscoveryClient();

            // Find all servers registered in the GDS.
            UAServerOnNetwork[] serverOnNetworkArray;
            try
            {
                globalDiscoveryClient.QueryServers(
                    gdsEndpointDescriptor:"opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer",
                    startingRecordId:0,
                    maximumRecordsToReturn:0,
                    applicationName:"",
                    applicationUriString:"",
                    productUriString:"",
                    serverCapabilities:new string[0],
                    lastCounterResetTime:out _,
                    serverOnNetworkArray:out serverOnNetworkArray);
            }
            catch (UAException uaException)
            {
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
                return;
            }

            // Display results
            foreach (UAServerOnNetwork serverOnNetwork in serverOnNetworkArray)
            {
                Console.WriteLine();
                Console.WriteLine("Server name: {0}", serverOnNetwork.ServerName);
                Console.WriteLine("Discovery URL string: {0}", serverOnNetwork.DiscoveryUrlString);
                Console.WriteLine("Server capabilities: {0}", serverOnNetwork.ServerCapabilities);
            }
        }
    }
}

' Shows how to find server applications that meet the specified filters, using the global discovery client.
'
' 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.Discovery
Imports OpcLabs.EasyOpc.UA.Gds
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace Gds._EasyUAGlobalDiscoveryClient
    Friend Class QueryServers
        Public Shared Sub Main1()

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

            ' Find all servers registered in the GDS.
            Dim serverOnNetworkArray() As UAServerOnNetwork = Nothing
            Try
                Dim lastCounterResetTime As DateTime
                globalDiscoveryClient.QueryServers(
                    gdsEndpointDescriptor:="opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer",
                    startingRecordId:=0,
                    maximumRecordsToReturn:=0,
                    applicationName:="",
                    applicationUriString:="",
                    productUriString:="",
                    serverCapabilities:=New String() {},
                    lastCounterResetTime:=lastCounterResetTime,
                    serverOnNetworkArray:=serverOnNetworkArray)
            Catch uaException As UAException
                Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
                Exit Sub
            End Try

            ' Display results
            For Each serverOnNetwork As UAServerOnNetwork In serverOnNetworkArray
                Console.WriteLine()
                Console.WriteLine("Server name: {0}", serverOnNetwork.ServerName)
                Console.WriteLine("Discovery URL string: {0}", serverOnNetwork.DiscoveryUrlString)
                Console.WriteLine("Server capabilities: {0}", serverOnNetwork.ServerCapabilities)
            Next serverOnNetwork
        End Sub
    End Class
End Namespace

COM

Object Pascal
Visual Basic (VB 6.)

// Shows how to find server applications that meet the specified filters, using the global discovery client.
//
// 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 QueryServers.Main;
var
  ApplicationName: WideString;
  ApplicationUriString: WideString;
  GlobalDiscoveryClient: OpcLabs_EasyOpcUA_TLB._EasyUAGlobalDiscoveryClient;
  GdsEndpointDescriptor: _UAEndpointDescriptor;
  I: integer;
  LastCounterResetTime: TDateTime;
  MaximumRecordsToReturn: Integer;
  ProductUriString: WideString;
  ServerCapabilities: array of string;
  ServerOnNetwork: _UAServerOnNetwork;
  ServerOnNetworkArray: OleVariant;
  StartingRecordId: Integer;
begin
  // Define which GDS we will work with.
  GdsEndpointDescriptor := CoUAEndpointDescriptor.Create;
  GdsEndpointDescriptor.UrlString := 'opc.tcp://opcua.demo-this.com:58810/GlobalDiscoveryServer';

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

  // Find all servers registered in the GDS.
  StartingRecordId := 0;
  MaximumRecordsToReturn := 0;
  ApplicationName := '';
  ApplicationUriString := '';
  ProductUriString := '';
  try
    GlobalDiscoveryClient.QueryServers(
      GdsEndpointDescriptor,
      StartingRecordId,
      MaximumRecordsToReturn,
      ApplicationName,
      ApplicationUriString,
      ProductUriString,
      ServerCapabilities,
      LastCounterResetTime,
      ServerOnNetworkArray);
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
    end;
  end;

  // Display results
  for I := VarArrayLowBound(ServerOnNetworkArray,1) to VarArrayHighBound(ServerOnNetworkArray,1) do
  begin
    ServerOnNetwork := IUnknown(ServerOnNetworkArray[I]) as _UAServerOnNetwork;
    WriteLn;
    WriteLn('Server name: ', ServerOnNetwork.ServerName);
    WriteLn('Discovery URL string: ', ServerOnNetwork.DiscoveryUrlString);
    WriteLn('Server capabilities: ', ServerOnNetwork.ServerCapabilities.ToString);
  end;

end;

REM Shows how to find server applications that meet the specified filters, using the global discovery client.
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 Visual Basic on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-VB .
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.

Private Sub EasyUAGlobalDiscoveryClient_QueryServers_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"
    
    ' Instantiate the global discovery client object
    Dim globalDiscoveryClient As New EasyUAGlobalDiscoveryClient
    
    ' Find all servers registered in the GDS.
    Dim startingRecordId As Integer: startingRecordId = 0
    Dim maximumRecordsToReturn As Integer: maximumRecordsToReturn = 0
    Dim applicationName As String: applicationName = ""
    Dim applicationUriString As String: applicationUriString = ""
    Dim productUriString As String: productUriString = ""
    Dim serverCapabilities: serverCapabilities = Array()
    Dim lastCounterResetTime As Date
    Dim serverOnNetworkArray As Variant
    On Error Resume Next
    Dim applicationId As UANodeId
    Call globalDiscoveryClient.QueryServers( _
      gdsEndpointDescriptor, _
      startingRecordId, _
      maximumRecordsToReturn, _
      applicationName, _
      applicationUriString, _
      productUriString, _
      serverCapabilities, _
      lastCounterResetTime, _
      serverOnNetworkArray)
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0
    
    ' Display results
    Dim i: For i = LBound(serverOnNetworkArray) To UBound(serverOnNetworkArray)
        Dim serverOnNetwork As UAServerOnNetwork
        Set serverOnNetwork = serverOnNetworkArray(i)
        OutputText = OutputText & vbCrLf
        OutputText = OutputText & "ServerName name: " & serverOnNetwork.ServerName & vbCrLf
        OutputText = OutputText & "Discovery URL string: " & serverOnNetwork.DiscoveryUrlString & vbCrLf
        OutputText = OutputText & "Server capabilities: " & serverOnNetwork.serverCapabilities.ToString & vbCrLf
    Next
End Sub

Python

Python (.NET)

# Shows how to find server applications that meet the specified filters, using the global discovery client.
#
# 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.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')

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

# Find all servers registered in the GDS.
try:
    _, _, serverOnNetworkArray = globalDiscoveryClient.QueryServers(
        gdsEndpointDescriptor,
        0,  # startingRecordId
        0,  # maximumRecordsToReturn
        '', # applicationName
        '', # applicationUriString
        '', # productUriString
        Array.Empty[String](),  # serverCapabilities
        DateTime(), # out lastCounterResetTime
        Array.Empty[UAServerOnNetwork]()) # out serverOnNetworkArray
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
for serverOnNetwork in serverOnNetworkArray:
    print()
    print('Server name: ', serverOnNetwork.ServerName, sep='')
    print('Discovery URL string: ', serverOnNetwork.DiscoveryUrlString, sep='')
    print('Server capabilities: ', serverOnNetwork.ServerCapabilities, sep='')

print()
print('Finished.')

Concepts

OPC UA Global Discovery Client

Fundamentals

OPC UA User Authentication (Client)