OPC Data Client - OPC DA - VB.NET - Configuring Settings and Timeouts of the Client Object

Example code written in VB.NET demonstrating configuration/optimization of the client engine is below.

Imports OpcLabs.EasyOpc.DataAccess

   Try
      'setup some constant values used by this example
      Const TimeoutSeconds As Integer = 3
      Const pc As String = "127.0.0.1"
      Const opc As String = "SWToolbox.TOPServer.V5"
      Const tag As String = "Channel1.Device1.Tag1"
      
      '
      'create our client object
      Dim EasyOPC As OpcLabs.EasyOpc.DataAccess.EasyDAClient = New OpcLabs.EasyOpc.DataAccess.EasyDAClient
      Dim ClientMode As EasyDAClientMode = New EasyDAClientMode
      Dim UpdateRates As EasyDAClientUpdateRates = New EasyDAClientUpdateRates
      Dim Timeouts As EasyDAClientTimeouts = New EasyDAClientTimeouts
      Dim HoldPeriods As EasyDAClientHoldPeriods = New EasyDAClientHoldPeriods
      
      '
      'Note: Some of the properties were previously set in the Options utility in version 3.02 of the Web Client
      'setup the mode and overall behavior of the opc data client component
      'From EasyDAClientModeClass
      ClientMode.AllowAsynchronousMethod = True 'When True, Async reads and write are allowed
      ClientMode.AllowSynchronousMethod = True 'When True, Sync reads and writes are allowed
      ClientMode.DesiredMethod = 1 'Determines if reads and writes are done async (1) or sync (0).
      
      '
      'From EasyDAClientHoldPeriods Class
      HoldPeriods.ItemDetach = TimeoutSeconds * 1000 'After an Item object is detached, connection will be maintained for this amount of time
      HoldPeriods.ServerDetach = TimeoutSeconds * 1000 'After an Item object is detached, connection will be maintained for the amount of time
      HoldPeriods.TopicRead = TimeoutSeconds * 1000 'After read, connection will be maintained at least for this amount of time
      HoldPeriods.TopicWrite = TimeoutSeconds * 1000 'After write, connection will be maintained at least for this amount of time
      
      '
      'From EasyDAClientTimeouts Class
      Timeouts.BrowseAccessPaths = 5000 'maximum time operation will wait for method to complete (success or failure)
      Timeouts.BrowseNodes = 5000 'maximum time operation will wait for BrowseBranches, BrowseLeaves and BrowseNodes methods to complete (success or failure)
      Timeouts.BrowseProperties = 5000 'maximum time operation will wait for method to complete (success or failure)
      Timeouts.BrowseServers = 5000 'maximum time operation will wait for any browse method to complete (success or failure)
      Timeouts.GetProperty = 5000 'maximum time operation will wait for any get property method to complete (success or failure)
      Timeouts.ReadItem = 5000 'maximum time operation will wait for any read method to complete (success or failure)
      Timeouts.WriteItem = 5000 'maximum time operation will wait for any write method to complete (success or failure)
      
      '
      'EasyDAClientUpdateRates Class
      UpdateRates.ReadAutomatic = 500 'After read, the initial update rate is set to this value
      UpdateRates.WriteAutomatic = 500 'After write, the initial update rate of the item is set to this value
      
      '
      'now to read the tag and to verify its success
      Dim theTag As DAVtq = EasyOPC.ReadItem(pc, opc, tag)
      
      MessageBox.Show("Channel1.Device1.Tag1 = " & theTag.Value.ToString & "(" & theTag.Quality.ToString & ") at " & theTag.Timestamp.ToString)
      
   Catch ex As Exception
      MessageBox.Show(ex.Message)
   End Try

A sample project is attached below.

• VB ConfigureSettingsBeforeReadingATag.zip