Discovers available OPC-UA servers on the network and returns information about them, specifying the discovery host, and whether the results should be flat.
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).
- flat
- Determines whether one element will be returned for each discovery URI.
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 hierarchical, i.e. each server is returned in one element, and the element contains all its discovery URLs.
//
// 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 Hierarchical()
{
// Instantiate the client object
var client = new EasyUAClient();
// Obtain collection of application elements
UADiscoveryElementCollection discoveryElementCollection;
try
{
discoveryElementCollection = client.DiscoverNetworkServers("opcua.demo-this.com", flat:false);
}
catch (UAException uaException)
{
Console.WriteLine("*** Failure: {0}", uaException.GetBaseException().Message);
return;
}
// Display results
foreach (UADiscoveryElement discoveryElement in discoveryElementCollection)
{
Console.WriteLine();
Console.WriteLine("Server name: {0}", discoveryElement.ServerName);
Console.WriteLine("Discovery URI strings:");
foreach (string discoveryUriString in discoveryElement.DiscoveryUriStrings)
Console.WriteLine(" {0}", discoveryUriString);
Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities);
}
}
}
}
' This example shows how to obtain information about OPC UA servers available on the network.
' The result is hierarchical, i.e. each server is returned in one element, and the element contains all its discovery URLs.
'
' 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 Hierarchical()
' 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", flat:=False)
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 strings:")
For Each discoveryUriString As String In discoveryElement.DiscoveryUriStrings
Console.WriteLine(" {0}", discoveryUriString)
Next discoveryUriString
Console.WriteLine("Server capabilities: {0}", discoveryElement.ServerCapabilities)
Next discoveryElement
End Sub
End Class
End Namespace
# This example shows how to obtain information about OPC UA servers available on the network.
# The result is hierarchical, i.e. each server is returned in one element, and the element contains all its discovery
# URLs.
#
# 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',
False) # flat=False
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 strings:')
for discoveryUriString in discoveryElement.DiscoveryUriStrings:
print(' ', discoveryUriString, sep='')
print('Server capabilities: ', discoveryElement.ServerCapabilities, 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