(Depreciated) Finds server applications that meet the specified filters.
Syntax
'Declaration
Sub QueryServers( _
ByVal As UAEndpointDescriptor, _
ByVal As Long, _
ByVal As Long, _
ByVal As String, _
ByVal As String, _
ByVal As String, _
ByVal As IEnumerable(Of String), _
ByRef As Date, _
ByRef () As UAServerOnNetwork _
)
'Usage
Dim instance As IEasyUAGlobalDiscoveryClient
Dim gdsEndpointDescriptor As UAEndpointDescriptor
Dim startingRecordId As Long
Dim maximumRecordsToReturn As Long
Dim applicationName As String
Dim applicationUriString As String
Dim productUriString As String
Dim serverCapabilities As IEnumerable(Of String)
Dim lastCounterResetTime As Date
Dim serverOnNetworkArray() As UAServerOnNetwork
instance.QueryServers(gdsEndpointDescriptor, startingRecordId, maximumRecordsToReturn, applicationName, applicationUriString, productUriString, serverCapabilities, lastCounterResetTime, serverOnNetworkArray)
Parameters
- gdsEndpointDescriptor
- Endpoint descriptor. Identifies the OPC-UA server. The server must be a Global Directory Server (GDS).
- startingRecordId
- Only records with an identifier greater than this number will be returned.
Specify 0 to start with the first record in the database. - maximumRecordsToReturn
- The maximum number of records to return in the response.
0 indicates that there is no limit. - applicationName
- The ApplicationName of the applications to return.
Supports the syntax used by the LIKE FilterOperator described in Part 4.
Not used if an empty string is specified. The filter is only applied to the default ApplicationName. - applicationUriString
- The ApplicationUri of the servers to return.
Supports the syntax used by the LIKE FilterOperator described in Part 4.
Not used if an empty string is specified. - productUriString
- The ProductUri of the servers to return.
Supports the syntax used by the LIKE FilterOperator described in Part 4.
Not used if an empty string is specified. - serverCapabilities
- The capabilities supported by the applications returned. If no server capabilities are provided this filter is not used.
- lastCounterResetTime
- The last time the counters were reset.
- serverOnNetworkArray
- A list of Servers which meet the criteria (OpcLabs.EasyOpc.UA.Discovery.UAServerOnNetwork).
Exceptions
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. |
Example
.NET
COM
// Shows how to find server applications that meet the specified filters, using the global discovery client.
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.
# 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.')
' Shows how to find server applications that meet the specified filters, using the global discovery client.
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
// Shows how to find server applications that meet the specified filters, using the global discovery client.
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.
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
Requirements
Target Platforms: .NET Framework: Windows 10 (selected versions), Windows 11 (selected versions), Windows Server 2016, Windows Server 2022; .NET: Linux, macOS, Microsoft Windows
See Also