QuickOPC User's Guide and Reference
Examples - OPC UA File Providers - Read sections of a file

The example below shows how to read different sections from an OPC UA file, using the file provider model.

// Shows how to read different sections from an OPC UA file, using the file provider model.

using System;
using System.IO;
using OpcLabs.BaseLib.Extensions.FileProviders;
using OpcLabs.EasyOpc.UA;
using OpcLabs.EasyOpc.UA.FileTransfer;

namespace UADocExamples.FileProviders._FileInfo2
{
    class ReadAndSeek
    {
        public static void Main1()
        {
            // Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            UAEndpointDescriptor endpointDescriptor = "opc.tcp://localhost:48030";

            // A node that represents an instance of OPC UA FileType object.
            UANodeDescriptor fileNodeDescriptor = "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile";
            
            // Instantiate the file transfer client object
            var fileTransferClient = new EasyUAFileTransferClient();

            Console.WriteLine("Getting file info...");
            IFileInfo2 fileInfo2 = fileTransferClient.GetFileInfo2(endpointDescriptor, fileNodeDescriptor);
            // From this point onwards, the code is independent of the concrete realization of the file provider, and would
            // be identical e.g. for files in the physical file system, if the corresponding file provider was used.

            // Open the file, read two separate sections of it, and close it.
            try
            {
                Console.WriteLine("Opening file...");
                using (Stream stream = fileInfo2.CreateReadStream())
                {
                    Console.WriteLine("Reading first section of a stream...");
                    var buffer1 = new byte[16];
                    int bytesRead1 = stream.Read(buffer1, 0, buffer1.Length);
                    Console.WriteLine($"{bytesRead1} bytes read, buffer: {BitConverter.ToString(buffer1)}");

                    Console.WriteLine("Reading second section of a stream...");
                    var buffer2 = new byte[10];
                    int bytesRead2 = stream.Read(buffer2, 0, buffer2.Length);
                    Console.WriteLine($"{bytesRead2} bytes read, buffer: {BitConverter.ToString(buffer2)}");

                    Console.WriteLine("Seeking...");
                    stream.Seek(100, SeekOrigin.Begin);

                    Console.WriteLine("Reading third section of a stream...");
                    var buffer3 = new byte[20];
                    int bytesRead3 = stream.Read(buffer3, 0, buffer3.Length);
                    Console.WriteLine($"{bytesRead3} bytes read, buffer: {BitConverter.ToString(buffer3)}");
                }
            }
            // Methods in the file provider model throw IOException and other exceptions, but not UAException.
            catch (Exception exception)
            {
                Console.WriteLine($"*** Failure: {exception.GetBaseException().Message}");
                return;
            }

            Console.WriteLine("Finished...");
        }
    }
}
# Shows how to read different sections from an OPC UA file, using the file provider model.

# The QuickOPC package is needed. Install it using "pip install opclabs_quickopc".
import opclabs_quickopc

# Import .NET namespaces.
from System import *
from System.IO import *
from System.Text import *
from OpcLabs.BaseLib.Extensions.FileProviders import *
from OpcLabs.EasyOpc.UA import *
from OpcLabs.EasyOpc.UA.FileTransfer import *
from OpcLabs.EasyOpc.UA.Navigation import *


# Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe).
endpointDescriptor = UAEndpointDescriptor('opc.tcp://localhost:48030')

# A node that represents an instance of OPC UA FileType object.
fileNodeDescriptor = UANodeDescriptor('nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile')

# Instantiate the file transfer client object.
fileTransferClient = EasyUAFileTransferClient()

print('Getting file info......')
fileInfo2 = IEasyUAFileTransferExtension.GetFileInfo2(fileTransferClient,
                                                      endpointDescriptor,
                                                      UANamedNodeDescriptor(fileNodeDescriptor))
# From this point onwards, the code is independent of the concrete realization of the file provider, and would
# be identical e.g. for files in the physical file system, if the corresponding file provider was used.

# Open the file, read two separate sections of it, and close it.
stream = None
try:
    print('Opening file...')
    stream = fileInfo2.CreateReadStream()

    print('Reading first section of a stream...')
    buffer1 = Array.CreateInstance(Byte, 16)
    bytesRead1, _ = stream.Read(buffer1, 0, buffer1.Length)
    print(bytesRead1, ' bytes read, buffer: ', BitConverter.ToString(buffer1), sep='')

    print('Reading second section of a stream...')
    buffer2 = Array.CreateInstance(Byte, 10)
    bytesRead2, _ = stream.Read(buffer2, 0, buffer2.Length)
    print(bytesRead2, ' bytes read, buffer: ', BitConverter.ToString(buffer2), sep='')

    print('Seeking...')
    stream.Seek(100, SeekOrigin.Begin)

    print('Reading third section of a stream...')
    buffer3 = Array.CreateInstance(Byte, 20)
    bytesRead3, _ = stream.Read(buffer3, 0, buffer3.Length)
    print(bytesRead3, ' bytes read, buffer: ', BitConverter.ToString(buffer3), sep='')

# Methods in the file provider model throw IOException and other exceptions, but not UAException.
except Exception as exception:
    print('*** Failure: ' + exception.GetBaseException().Message)
    exit()

finally:
    stream and stream.Dispose()

print()
print('Finished.')
' Shows how to read different sections from an OPC UA file, using the file provider model.

Imports System.IO
Imports OpcLabs.BaseLib.Extensions.FileProviders
Imports OpcLabs.EasyOpc.UA
Imports OpcLabs.EasyOpc.UA.FileTransfer

Namespace FileProviders._FileInfo2

    Friend Class ReadAndSeek

        Public Shared Sub Main1()

            ' Unified Automation .NET based demo server (UaNETServer/UaServerNET.exe)
            Dim endpointDescriptor As UAEndpointDescriptor = "opc.tcp://localhost:48030"

            ' A node that represents an instance of OPC UA FileType object.
            Dim fileNodeDescriptor As UANodeDescriptor =
                "nsu=http://www.unifiedautomation.com/DemoServer/ ;s=Demo.Files.TextFile"

            ' Instantiate the file transfer client object
            Dim fileTransferClient = New EasyUAFileTransferClient

            Console.WriteLine("Getting file info...")
            Dim fileInfo2 As IFileInfo2 =
                fileTransferClient.GetFileInfo2(endpointDescriptor, fileNodeDescriptor)
            ' From this point onwards, the code is independent of the concrete realization of the file provider, and would
            ' be identical e.g. for files in the physical file system, if the corresponding file provider was used.

            ' Open the file, read two separate sections of it, and close it.
            Try
                Console.WriteLine("Opening file...")
                Using stream As Stream = fileInfo2.CreateReadStream()
                    Console.WriteLine("Reading first section of a stream...")
                    Dim buffer1(16 - 1) As Byte
                    Dim bytesRead1 As Integer = stream.Read(buffer1, 0, buffer1.Length)
                    Console.WriteLine($"{bytesRead1} bytes read, buffer: {BitConverter.ToString(buffer1)}")

                    Console.WriteLine("Reading second section of a stream...")
                    Dim buffer2(10 - 1) As Byte
                    Dim bytesRead2 As Integer = stream.Read(buffer2, 0, buffer2.Length)
                    Console.WriteLine($"{bytesRead2} bytes read, buffer: {BitConverter.ToString(buffer2)}")

                    Console.WriteLine("Seeking...")
                    stream.Seek(100, SeekOrigin.Begin)

                    Console.WriteLine("Reading third section of a stream...")
                    Dim buffer3(20 - 1) As Byte
                    Dim bytesRead3 As Integer = stream.Read(buffer3, 0, buffer3.Length)
                    Console.WriteLine($"{bytesRead3} bytes read, buffer: {BitConverter.ToString(buffer3)}")
                End Using

                ' Methods in the file provider model throw IOException and other exceptions, but not UAException.
            Catch exception As Exception
                Console.WriteLine("*** Failure: {0}", exception.GetBaseException.Message)
                Exit Sub
            End Try

            Console.WriteLine("Finished...")
        End Sub
    End Class
End Namespace

 

See Also

Examples - OPC UA File Transfer

Conceptual