DiscoverLocalServers Method (EasyUAClientCore)

Discovers available OPC-UA servers and returns information about them, using the default discovery host.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<ElementsNotNullAttribute()>
<NotNullAttribute()>
Public Function DiscoverLocalServers() As UADiscoveryElementCollection

'Usage
 
Dim instance As EasyUAClientCore
Dim value As UADiscoveryElementCollection
 
value = instance.DiscoverLocalServers()

[ElementsNotNull()]
[NotNull()]
public UADiscoveryElementCollection DiscoverLocalServers()

[ElementsNotNull()]
[NotNull()]
public:
UADiscoveryElementCollection^ DiscoverLocalServers();

Return Value

Returns a collection of application elements (usually servers, OpcLabs.EasyOpc.UA.Discovery.UADiscoveryElement).

Remarks

This method uses the so-called Local Discovery Server (LDS). You can influence how the discovery works using the properties in SharedParameters. The name of the machine that runs the discovery is determined by OpcLabs.EasyOpc.UA.Engine.EasyUAInstanceParameters.DiscoveryHost in InstanceParameters, and defaults to "localhost".

Invokes the FindServers service.

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

Example

// This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
//
// Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

using System;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.Discovery;
using OpcLabs.EasyOpc.UA.OperationModel;

namespace UADocExamples._EasyUAClient
{
    class DiscoverLocalServers
    {
        public static void Overload1()
        {
            // Instantiate the client object.
            var client = new EasyUAClient();

            // Obtain collection of server elements.
            UADiscoveryElementCollection discoveryElementCollection;
            try
            {
                discoveryElementCollection = client.DiscoverLocalServers("opcua.demo-this.com");
            }
            catch (UAException uaException)
            {
                Console.WriteLine($"*** Failure: {uaException.GetBaseException().Message}");
                return;
            }

            // Display results.
            foreach (UADiscoveryElement discoveryElement in discoveryElementCollection)
                Console.WriteLine($"discoveryElementCollection[\"{discoveryElement.DiscoveryUriString}\"].ApplicationUriString: {discoveryElement.ApplicationUriString}");

            
            // Example output:
            //
            //discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
            //discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
            //discoveryElementCollection["https://opcua.demo-this.com:51212/UA/SampleServer/"].ApplicationUriString: urn: DEMO - 5:UA Sample Server
            //discoveryElementCollection["http://opcua.demo-this.com:62543/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn: opcua.demo - this.com:Quickstart Alarm Condition Server
            //discoveryElementCollection["opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn: opcua.demo - this.com:Quickstart Alarm Condition Server
        }
    }
}

# This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
#
# Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

#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 server elements.
try {
    $discoveryElementCollection = [IEasyUAClientExtension]::DiscoverLocalServers($client, "opcua.demo-this.com")
}
catch [UAException] {
    Write-Host "*** Failure: $($PSItem.Exception.GetBaseException().Message)"
    return
}

# Display results.
foreach ($discoveryElement in $discoveryElementCollection) {
    Write-Host "discoveryElementCollection[`"$($discoveryElement.DiscoveryUriString)`"].ApplicationUriString: $($discoveryElement.ApplicationUriString)"
}


# Example output:
#
#discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["https://opcua.demo-this.com:51212/UA/SampleServer/"].ApplicationUriString: urn:DEMO-5:UA Sample Server
#discoveryElementCollection["http://opcua.demo-this.com:62543/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn:opcua.demo-this.com:Quickstart Alarm Condition Server
#discoveryElementCollection["opc.tcp://opcua.demo-this.com:62544/Quickstarts/AlarmConditionServer"].ApplicationUriString: urn:opcua.demo-this.com:Quickstart Alarm Condition Server

# This example shows how to obtain application URLs of all OPC Unified Architecture servers on the specified host.
#
# 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 .
# 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.OperationModel import *


# Instantiate the client object.
client = EasyUAClient()

# Obtain collection of server elements.
try:
    discoveryElementCollection = IEasyUAClientExtension.DiscoverLocalServers(client, 'opcua.demo-this.com')
except UAException as uaException:
    print('*** Failure: ' + uaException.GetBaseException().Message)
    exit()

# Display results.
for discoveryElement in discoveryElementCollection:
    print('DiscoveryElementCollection["', discoveryElement.DiscoveryUriString, '"].ApplicationUriString: ', 
          discoveryElement.ApplicationUriString, sep='')

' This example shows how to obtain application URLs of all OPC Unified Architecture servers on a given machine.
'
' Find all latest examples here: https://opclabs.doc-that.com/files/onlinedocs/OPCLabs-OpcStudio/Latest/examples.html .

Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.Discovery
Imports OpcLabs.EasyOpc.UA.OperationModel

Namespace _EasyUAClient
    Friend Class DiscoverLocalServers
        Public Shared Sub Overload1()
            ' Instantiate the client object
            Dim client = New EasyUAClient()

            ' Obtain collection of server elements
            Dim discoveryElementCollection As UADiscoveryElementCollection
            Try
                discoveryElementCollection = client.DiscoverLocalServers("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("discoveryElementCollection[""{0}""].ApplicationUriString: {1}", _
                                  discoveryElement.DiscoveryUriString, discoveryElement.ApplicationUriString)
            Next discoveryElement

            ' Example output:
            'discoveryElementCollection["opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"].ApplicationUriString: urn:Test-PC:UA Sample Server
            'discoveryElementCollection["http://opcua.demo-this.com:51211/UA/SampleServer"].ApplicationUriString: urn:Test-PC:UA Sample Server
        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

Reference

EasyUAClientCore Class
EasyUAClientCore Members
DiscoveryTimeout Property

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