.NET VB form hangs during execution process

Question

Hi,
I have a .NET VB application running on a windows server. My VB is connected to a PLC, and my VB service suppose to read data from PLC. During the execution of the VB code, my application hangs if the PLC is disconnected and remain in hung state even though the PLC is connected back.
I have used a catch statement, but seems like its not catching any threads.

Answer 1

I think the Problem is that MicroLogix is not connected directly to the SQL server but its connected through a network interface module.
My service stops responding once it goes to the Step PLC_Read() and its not even going to next step as my PLC is powered off, but when the PLC is back UP and running again, still the service is not responding.

Please see My code

 Imports System.Data.SqlClient
   Imports ABLink
   Public Class Form1
   Public PLC_Compactor As New Controller

    Public MyTag As New Tag
    '**********************************
    '* initialize Threading Timer
    Private oTimer As Threading.Timer

    '**********************************
    '* Define Registers
    Dim length, breakpoint As Integer
    Dim DayValueHold As Integer = 1
    Dim DateStored, TimeStored, DateTimeCurrent, DateOfDumpFormatted, TimeOfDumpFormatted As String

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        ' Add code here to start your service. This method should set things
        ' in motion so your service can do its work.
        '**********************************
        '* CONNECT TO PLC
        PLC_Compactor.CPUType = Controller.CPU.SLC
        PLC_Compactor.DriverType = Controller.Driver.NETENI

        PLC_Compactor.IPAddress = "192.168.4.190"
        ' PLC_Compactor.Path = "0.0.0.0"
        PLC_Compactor.Timeout = 3000
        PLC_Compactor.Connect()
    End Sub


    Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
        Try
            If (PLC_Compactor.Connect() = ResultCode.E_SUCCESS) Then
                PLC_Read()
                If PLC_Trigger <> 0 Then
                WriteToPLC_UpdateTime()
                    ConvertToDateFormat(DateOfDump, DateOfDumpFormatted)
                    ConvertToTimeFormat(TimeOfDump, TimeOfDumpFormatted)
                    WriteToSQL()
                    WriteToPLC_ZeroTrigger()
                End If
            End If
        Catch ex As Exception
            ErrorMessageAdd("PLC Connect Fail, " & ex.Message)
        End Try
    End Sub

Thank you

Answer 2

I noticed that you made a connection in the Form.load event,

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
        ...  
        PLC_Compactor.Connect()  
    End Sub  

But this event is loaded only once before the form is first displayed. If you need to establish a connection again, you can consider putting it into Timer.Tick methods.

For example.

Private Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick  
        If Not ( "something like PLC_Compactor isConnected?") Then  
            PLC_Compactor.Connect()  
        End If  
        Try  
            ...      
    End Sub  

Hope it could be helpful.
Note: Due to the lack of understanding of ‘ABLink’, the above code has not been tested.

Best Regards,
Xingyu Zhao

If the answer is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.