QuickOPC User's Guide and Reference
DiscoverNetworkServers(IEasyUAClient,String,Boolean) Method
Example 



OpcLabs.EasyOpcUA Assembly > OpcLabs.EasyOpc.UA Namespace > IEasyUAClientExtension Class > DiscoverNetworkServers Method : DiscoverNetworkServers(IEasyUAClient,String,Boolean) Method
The client object that will perform the operation.
The name of the machine that runs the discovery server that will be used for discovery task.
Determines whether one element will be returned for each discovery URI.
Discovers available OPC-UA servers on the network and returns information about them.
Syntax
'Declaration
 
<ExtensionAttribute()>
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Overloads Shared Function DiscoverNetworkServers( _
   ByVal client As IEasyUAClient, _
   ByVal discoveryHost As String, _
   ByVal flat As Boolean _
) As UADiscoveryElementCollection
'Usage
 
Dim client As IEasyUAClient
Dim discoveryHost As String
Dim flat As Boolean
Dim value As UADiscoveryElementCollection
 
value = IEasyUAClientExtension.DiscoverNetworkServers(client, discoveryHost, flat)
[Extension()]
[ElementsNotNull()]
[NotNull()]
public static UADiscoveryElementCollection DiscoverNetworkServers( 
   IEasyUAClient client,
   string discoveryHost,
   bool flat
)
[Extension()]
[ElementsNotNull()]
[NotNull()]
public:
static UADiscoveryElementCollection^ DiscoverNetworkServers( 
   IEasyUAClient^ client,
   String^ discoveryHost,
   bool flat
) 

Parameters

client
The client object that will perform the operation.
discoveryHost
The name of the machine that runs the discovery server that will be used for discovery task.
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).
Exceptions
ExceptionDescription

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.

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

This method uses the so-called Local Discovery Server with Multicast Extensions (LDS-NE). You can influence how the discovery works using the properties in SharedParameters.

Invokes the FindServersOnNetwork service.

See also in Knowledge Base: Technical note-OPC UA Discovery in QuickOPC.

When the flat parameter is false, the discovery query returns one OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement for each application found, and its OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriStrings property contains one or more application discovery URLs.

When the flat parameter is true, the discovery query returns one OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement for each discovery URL of each application found. In this case, the OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriStrings property of each returned application element contains precisely one string, and you can therefore use the OpcLabs.EasyOpc.UA.Discovery.IUAReadOnlyApplicationElement.DiscoveryUriString property instead to obtain the discovery URL.

Example

.NET

// 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.

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.

# 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.')
' 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.

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
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