Read Method (_EasyUAClient)

Reads data of a node's Value attribute, using an endpoint descriptor and a node Id.

Syntax

Visual Basic
C#
C++/CLI

'Declaration
 
<NotNullAttribute()>
Function Read( _
   ByVal endpointDescriptorString As String, _
   ByVal nodeDescriptorString As String _
) As UAAttributeData

'Usage
 
Dim instance As _EasyUAClient
Dim endpointDescriptorString As String
Dim nodeDescriptorString As String
Dim value As UAAttributeData
 
value = instance.Read(endpointDescriptorString, nodeDescriptorString)

[NotNull()]
UAAttributeData Read( 
   string endpointDescriptorString,
   string nodeDescriptorString
)

[NotNull()]
UAAttributeData^ Read( 
   String^ endpointDescriptorString,
   String^ nodeDescriptorString
)

Parameters

endpointDescriptorString: Endpoint descriptor. Identifies the OPC-UA server.
nodeDescriptorString: Node descriptor. Identifies the node in OPC server's address space.

Return Value

Returns an attribute data object that stores the value of an attribute, together with status code and timestamps.

Remarks

You can obtain nodeDescriptorString e.g. by calling one of the browsing methods on OpcLabs.EasyOpc.UA.EasyUAClientCore object.

Example

// This example shows how to read and display data of an attribute (value, timestamps, and status code).

#include "stdafx.h"    // Includes "QuickOpc.h", and other commonly used files
#include "Read.h"

namespace _EasyUAClient
{
    void Read::Main()
    {
        // Initialize the COM library
        CoInitializeEx(NULL, COINIT_MULTITHREADED);
        {
            // Instantiate the client object
            _EasyUAClientPtr ClientPtr(__uuidof(EasyUAClient));

            // Obtain attribute data. By default, the Value attribute of a node will be read.
            _UAAttributeDataPtr AttributeDataPtr = ClientPtr->Read(
                //L"http://opcua.demo-this.com:51211/UA/SampleServer", 
                L"opc.tcp://opcua.demo-this.com:51210/UA/SampleServer",
                L"nsu=http://test.org/UA/Data/ ;i=10853");
    
            // Display results
            _variant_t vString;
            vString.ChangeType(VT_BSTR, &AttributeDataPtr->Value);
            _tprintf(_T("Value: %s\n"), (LPCTSTR)CW2CT((_bstr_t)vString));
            vString.ChangeType(VT_BSTR, &_variant_t(AttributeDataPtr->ServerTimestamp, VT_DATE));
            _tprintf(_T("ServerTimestamp: %s\n"), (LPCTSTR)CW2CT((_bstr_t)vString));
            vString.ChangeType(VT_BSTR, &_variant_t(AttributeDataPtr->SourceTimestamp, VT_DATE));
            _tprintf(_T("SourceTimestamp: %s\n"), (LPCTSTR)CW2CT((_bstr_t)vString));
            _tprintf(_T("StatusCode: %s\n"), (LPCTSTR)CW2CT(AttributeDataPtr->StatusCode->ToString));

            // Example output:
            //
            //Value: -2.230064E-31
            //ServerTimestamp: 11/6/2011 1:34:30 PM
            //SourceTimestamp: 11/6/2011 1:34:30 PM
            //StatusCode: Good

        }
         // Release all interface pointers BEFORE calling CoUninitialize()
        CoUninitialize();
    }
}

// This example shows how to read and display data of an attribute (value,
// timestamps, and status code).

class procedure Read.Main;
var
  Client: EasyUAClient;
  AttributeData: _UAAttributeData;
begin
  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  // Obtain attribute data. By default, the Value attribute of a node will be
  // read.
  AttributeData := Client.Read_(
    //'http://opcua.demo-this.com:51211/UA/SampleServer',
    'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer',
    'nsu=http://test.org/UA/Data/ ;i=10853');

  // Display results
  WriteLn('Value: ', AttributeData.Value);
  WriteLn('ServerTimestamp: ', DateTimeToStr(AttributeData.ServerTimestamp));
  WriteLn('SourceTimestamp: ', DateTimeToStr(AttributeData.SourceTimestamp));
  WriteLn('StatusCode: ', AttributeData.StatusCode.ToString);

  // Example output:
  //
  //Value: -2.230064E-31
  //ServerTimestamp: 11/6/2011 1:34:30 PM
  //SourceTimestamp: 11/6/2011 1:34:30 PM
  //StatusCode: Good
end;

// This example shows how to read and display data of an attribute (value,
// timestamps, and status code).

class procedure Read.Main;
var
  Client: OpcLabs_EasyOpcUA_TLB._EasyUAClient;
  AttributeData: _UAAttributeData;
begin
  // Instantiate the client object
  Client := CoEasyUAClient.Create;

  // Obtain attribute data. By default, the Value attribute of a node will be
  // read.
  try
    AttributeData := Client.Read(
      //'http://opcua.demo-this.com:51211/UA/SampleServer',
      //'https://opcua.demo-this.com:51212/UA/SampleServer/',
      'opc.tcp://opcua.demo-this.com:51210/UA/SampleServer',
      'nsu=http://test.org/UA/Data/ ;i=10853');
  except
    on E: EOleException do
    begin
      WriteLn(Format('*** Failure: %s', [E.GetBaseException.Message]));
      Exit;
    end;
  end;

  // Display results
  WriteLn('Value: ', AttributeData.Value);
  WriteLn('ServerTimestamp: ', DateTimeToStr(AttributeData.ServerTimestamp));
  WriteLn('SourceTimestamp: ', DateTimeToStr(AttributeData.SourceTimestamp));
  WriteLn('StatusCode: ', AttributeData.StatusCode.ToString);

  // Example output:
  //
  //Value: -2.230064E-31
  //ServerTimestamp: 11/6/2011 1:34:30 PM
  //SourceTimestamp: 11/6/2011 1:34:30 PM
  //StatusCode: Good
end;

// This example shows how to read and display data of an attribute (value, timestamps, and status code).

// Instantiate the client object
$Client = new COM("OpcLabs.EasyOpc.UA.EasyUAClient");

// Obtain attribute data. By default, the Value attribute of a node will be read.
try
{
    $AttributeData = $Client->Read(
        //"http://opcua.demo-this.com:51211/UA/SampleServer", 
        "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", 
        "nsu=http://test.org/UA/Data/ ;i=10853");
}
catch (com_exception $e)
{
    printf("*** Failure: %s\n", $e->getMessage());
    Exit();
}

// Display results
printf("Value: %s\n", $AttributeData->Value);
printf("ServerTimestamp: %s\n", $AttributeData->ServerTimestamp);
printf("SourceTimestamp: %s\n", $AttributeData->SourceTimestamp);
printf("StatusCode: %s\n", $AttributeData->StatusCode);

// Example output:
//
//Value: -2.230064E-31
//ServerTimestamp: 11/6/2011 1:34:30 PM
//SourceTimestamp: 11/6/2011 1:34:30 PM
//StatusCode: Good

// This example shows how to read and display data of an attribute (value, timestamps, and status code).

mle_outputtext.Text = ""

// Instantiate the client object
OLEObject client
client = CREATE OLEObject
client.ConnectToNewObject("OpcLabs.EasyOpc.UA.EasyUAClient")

// Obtain attribute data. By default, the Value attribute of a node will be read.
OLEObject attributeData
TRY
    attributeData = client.Read("http://opcua.demo-this.com:51211/UA/SampleServer", "nsu=http://test.org/UA/Data/ ;i=10853")        // or "opc.tcp://opcua.demo-this.com:51210/UA/SampleServer"
CATCH (OLERuntimeError oleRuntimeError)
    mle_outputtext.Text = mle_outputtext.Text + "*** Failure: " + oleRuntimeError.Description + "~r~n"
    RETURN
END TRY

// Display results
mle_outputtext.Text = mle_outputtext.Text + "Value: " + String(attributeData.value) + "~r~n"
mle_outputtext.Text = mle_outputtext.Text + "ServerTimestamp: " + String(attributeData.ServerTimestamp) + "~r~n"
mle_outputtext.Text = mle_outputtext.Text + "SourceTimestamp: " + String(attributeData.SourceTimestamp) + "~r~n"
mle_outputtext.Text = mle_outputtext.Text + "StatusCode: " + String(attributeData.StatusCode) + "~r~n"

// Example output:
//
//Value: -2.230064E-31
//ServerTimestamp: 11/6/2011 1:34:30 PM
//SourceTimestamp: 11/6/2011 1:34:30 PM
//StatusCode: Good

# This example shows how to read and display data of an attribute (value, timestamps, and status code).

# The Python for Windows (pywin32) extensions package is needed. Install it using "pip install pypiwin32".
# CAUTION: We now recommend using Python.NET package instead. Full set of examples with Python.NET is available!
import win32com.client
from pywintypes import com_error

# Instantiate the client object
client = win32com.client.Dispatch('OpcLabs.EasyOpc.UA.EasyUAClient') 

# Obtain attribute data. By default, the Value attribute of a node will be read.
try:
    attributeData = client.Read('opc.tcp://opcua.demo-this.com:51210/UA/SampleServer',
                                'nsu=http://test.org/UA/Data/ ;i=10853')
except com_error as e:
    print('*** Failure: ' + e.args[2][1] + ': ' + e.args[2][2])
    exit()

# Display results
print('Value: ', attributeData.Value)
print('ServerTimestamp: ', attributeData.ServerTimestamp)
print('SourceTimestamp: ', attributeData.SourceTimestamp)
print('StatusCode: ', attributeData.StatusCode)

# Example output:
#
#Value: -2.230064E-31
#ServerTimestamp: 11/6/2011 1:34:30 PM
#SourceTimestamp: 11/6/2011 1:34:30 PM
#StatusCode: Good

Rem This example shows how to read and display data of an attribute (value, timestamps, and status code).

Public Sub Read_Main_Command_Click()
    OutputText = ""

    ' Instantiate the client object
    Dim Client As New EasyUAClient

    ' Obtain attribute data. By default, the Value attribute of a node will be read.
    On Error Resume Next
    Dim AttributeData As UAAttributeData
    Set AttributeData = Client.Read("opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", _
                                    "nsu=http://test.org/UA/Data/ ;i=10853")
    If Err.Number <> 0 Then
        OutputText = OutputText & "*** Failure: " & Err.Source & ": " & Err.Description & vbCrLf
        Exit Sub
    End If
    On Error GoTo 0

    ' Display results
    OutputText = OutputText & "Value: " & AttributeData.value & vbCrLf
    OutputText = OutputText & "ServerTimestamp: " & AttributeData.ServerTimestamp & vbCrLf
    OutputText = OutputText & "SourceTimestamp: " & AttributeData.SourceTimestamp & vbCrLf
    OutputText = OutputText & "StatusCode: " & AttributeData.StatusCode & vbCrLf

    ' Example output:
    '
    'Value: -2.230064E-31
    'ServerTimestamp: 11/6/2011 1:34:30 PM
    'SourceTimestamp: 11/6/2011 1:34:30 PM
    'StatusCode: Good
End Sub

Rem This example shows how to read and display data of an attribute (value, timestamps, and status code).

Option Explicit

' Instantiate the client object
Dim Client: Set Client = CreateObject("OpcLabs.EasyOpc.UA.EasyUAClient")

' Obtain attribute data. By default, the Value attribute of a node will be read.
On Error Resume Next
Dim AttributeData: Set AttributeData = Client.Read("opc.tcp://opcua.demo-this.com:51210/UA/SampleServer", _
                                                   "nsu=http://test.org/UA/Data/ ;i=10853")
If Err.Number <> 0 Then
    WScript.Echo "*** Failure: " & Err.Source & ": " & Err.Description
    WScript.Quit
End If
On Error Goto 0

' Display results
WScript.Echo "Value: " & AttributeData.Value
WScript.Echo "ServerTimestamp: " & AttributeData.ServerTimestamp
WScript.Echo "SourceTimestamp: " & AttributeData.SourceTimestamp
WScript.Echo "StatusCode: " & AttributeData.StatusCode

' Example output:
'
'Value: -2.230064E-31
'ServerTimestamp: 11/6/2011 1:34:30 PM
'SourceTimestamp: 11/6/2011 1:34:30 PM
'StatusCode: Good

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

_EasyUAClient Interface
_EasyUAClient Members

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