Discovers available OPC-UA servers on the network and returns information about them, using the specified discovery host.
Syntax
Parameters
- client
- The client object that will perform the operation.
This is typically the EasyUAClient object.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
- discoveryHost
- The name of the machine that runs the discovery server that will be used for discovery task.
The value of this parameter cannot be null
(Nothing
in Visual Basic).
Return Value
Returns a collection of application elements (servers,
OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement).
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 |
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
// This example shows how to obtain information about OPC UA servers available on the network.
// The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers.
//
// 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.OperationModel;
namespace UADocExamples._EasyUAClient
{
partial class DiscoverNetworkServers
{
public static void Main1()
{
// Instantiate the client object.
var client = new EasyUAClient();
// Obtain collection of application elements.
UADiscoveryElementCollection discoveryElementCollection;
try
{
discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com");
}
catch (UAException uaException)
{
Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
return;
}
// Display results.
foreach (UADiscoveryElement discoveryElement in discoveryElementCollection)
{
Console.WriteLine();
Console.WriteLine($"Server name: {discoveryElement.ServerName}");
Console.WriteLine($"Discovery URI string: {discoveryElement.DiscoveryUriString}");
Console.WriteLine($"Server capabilities: {discoveryElement.ServerCapabilities}");
Console.WriteLine($"Application URI string: {discoveryElement.ApplicationUriString}");
Console.WriteLine($"Product URI string: {discoveryElement.ProductUriString}");
}
}
}
}
# This example shows how to obtain information about OPC UA servers available on the network.
# The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .
# OPC client and subscriber examples in PowerShell on GitHub: https://github.com/OPCLabs/Examples-QuickOPC-PowerShell .
# 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.
#requires -Version 5.1
using namespace OpcLabs.EasyOpc.UA
using namespace OpcLabs.EasyOpc.UA.Discovery
using namespace OpcLabs.EasyOpc.UA.OperationModel
# The path below assumes that the current directory is [ProductDir]/Examples-NET/PowerShell/Windows .
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUA.dll"
Add-Type -Path "../../../Components/Opclabs.QuickOpc/net472/OpcLabs.EasyOpcUAComponents.dll"
# Instantiate the client object.
$client = New-Object EasyUAClient
# Obtain collection of application elements.
try {
$discoveryElementCollection = [IEasyUAClientExtension]::DiscoverNetworkServers($client, "opcua.demo-this.com")
}
catch [UAException] {
Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
return
}
# Display results.
foreach ($discoveryElement in $discoveryElementCollection) {
Write-Host
Write-Host "Server name: $($discoveryElement.ServerName)"
Write-Host "Discovery URI string: $($discoveryElement.DiscoveryUriString)"
Write-Host "Server capabilities: $($discoveryElement.ServerCapabilities)"
Write-Host "Application URI string: $($discoveryElement.ApplicationUriString)"
Write-Host "Product URI string: $($discoveryElement.ProductUriString)"
}
' This example shows how to obtain information about OPC UA servers available on the network.
' The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers.
'
' 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.OperationModel
Namespace _EasyUAClient
Partial Friend Class DiscoverNetworkServers
Public Shared Sub Main1()
' Instantiate the client object
Dim client = New EasyUAClient()
' Obtain collection of application elements
Dim discoveryElementCollection As UADiscoveryElementCollection
Try
discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com")
Catch uaException As UAException
Console.WriteLine("*** Failure: {0}", uaException.GetBaseException.Message)
Exit Sub
End Try
' Display results
For Each discoveryElement As UADiscoveryElement In discoveryElementCollection
Console.WriteLine()
Console.WriteLine("Server name: {0}", discoveryElement.ServerName)
Console.WriteLine("Discovery URI string: {0}", discoveryElement.DiscoveryUriString)
Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities)
Console.WriteLine("Application URI string: {0}", discoveryElement.ApplicationUriString)
Console.WriteLine("Product URI string: {0}", discoveryElement.ProductUriString)
Next discoveryElement
End Sub
End Class
End Namespace
// This example shows how to obtain information about OPC UA servers available on the network.
//
// 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 DiscoverNetworkServers.Main;
var
Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
Count: Cardinal;
Element: OleVariant;
DiscoveryElement: _UADiscoveryElement;
DiscoveryElementEnumerator: IEnumVariant;
DiscoveryElements: _UADiscoveryElementCollection;
begin
// Instantiate the client object
Client := CoEasyUAClient.Create;
// Obtain collection of application elements
try
DiscoveryElements := Client.DiscoverNetworkServers(Unassigned, 'opcua.demo-this.com');
except
on E: EOleException do
begin
WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
Exit;
end;
end;
// Display results
DiscoveryElementEnumerator := DiscoveryElements.GetEnumerator;
while (DiscoveryElementEnumerator.Next(1, Element, Count) = S_OK) do
begin
DiscoveryElement := IUnknown(Element) as _UADiscoveryElement;
WriteLn;
WriteLn('Server name: ', DiscoveryElement.ServerName);
WriteLn('Discovery URI string: ', DiscoveryElement.DiscoveryUriString);
WriteLn('Server capabilities: ', DiscoveryElement.ServerCapabilities.ToString);
end;
end;
REM This example shows how to obtain information about OPC UA servers available on the network.
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.
Public Sub DiscoverNetworkServers_Main_Command_Click()
OutputText = ""
' Instantiate the client object
Dim Client As New EasyUAClient
' Obtain collection of application elements
On Error Resume Next
Dim DiscoveryElementCollection As UADiscoveryElementCollection
Set DiscoveryElementCollection = Client.DiscoverNetworkServers(Nothing, "opcua.demo-this.com")
If Err.Number <> 0 Then
OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
Exit Sub
End If
On Error GoTo 0
' Display results
Dim DiscoveryElement As UADiscoveryElement: For Each DiscoveryElement In DiscoveryElementCollection
OutputText = OutputText & vbCrLf
OutputText = OutputText & "Server name: " & DiscoveryElement.ServerName & vbCrLf
OutputText = OutputText & "Discovery URI string: " & DiscoveryElement.DiscoveryUriString & vbCrLf
OutputText = OutputText & "Server capabilities: " & DiscoveryElement.serverCapabilities.ToString & vbCrLf
Next
End Sub
# This example shows how to obtain information about OPC UA servers available on the network.
# The result is flat, i.e. each discovery URL is returned in separate element, with possible repetition of the servers.
#
# 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 OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.Discovery import *
from OpcLabs.EasyOpc.UA.OperationModel import *
# Instantiate the client object.
client = EasyUAClient()
# Obtain collection of application elements.
try:
discoveryElementCollection = IEasyUAClientExtension.DiscoverNetworkServers(client, 'opcua.demo-this.com')
except UAException as uaException:
print('*** Failure: ' + uaException.GetBaseException().Message)
exit()
# Display results.
for discoveryElement in discoveryElementCollection:
print()
print('Server name: ', discoveryElement.ServerName, sep='')
print('Discovery URI string: ', discoveryElement.DiscoveryUriString, sep='')
print('Server capabilities: ', discoveryElement.ServerCapabilities, sep='')
print('Application URI string: ', discoveryElement.ApplicationUriString, sep='')
print('Product URI string: ', discoveryElement.ProductUriString, 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
See Also