vb6 multithread runs 21 times then stops and errors

Hi,
I have a project that has to read the usb port all the time and look at the data to parse it out and put some strings in a file.
The following code will read the usb port and put the data into a circular buffer so that the top level application can read the data and then process it.
This code seems to run 21 times before it just exits.
I do not know what would cause such behavior,
Can anyone offer any suggestions?
Thanks,
Martin

Code:

---

Public Sub WaitForUsbRet()
Dim EventObject As Long
Dim Result As Long
Dim res2 As Integer
Dim Security As SECURITY_ATTRIBUTES
Dim RecBuffer(65) As Byte
Dim rdNum As Long
Dim i As Integer
Dim res3 As Long
res2 = 1

    Security.lpSecurityDescriptor = 0
    Security.bInheritHandle = CInt(True)
    Security.nLength = Len(Security)
       
    EventObject = CreateEvent(Security, CInt(True), CInt(False), "rdUsb")
    HIDOverlapped.Offset = 0
    HIDOverlapped.OffsetHigh = 0
    HIDOverlapped.hEvent = EventObject

    Do
        Form1.ShpStatus.BackColor = Form1.ShpStatus.BackColor + 1
        DoEvents
        RecBuffer(4) = 0
        RecBuffer(5) = 0
        Result = ReadFile _
        (HIDHandle, _
        RecBuffer(0), _
        CLng(Capabilities.InputReportByteLength), _
        rdNum, _
        HIDOverlapped)

        Form1.lstBoxRec.AddItem "Res=" & Result & " rdnum=" & rdNum & " hid=" & HIDOverlapped.Internal

        Result = WaitForSingleObject(EventObject, 500)
       
        Form1.lstBoxRec.AddItem "Res2=" & Result & " err=" & GetLastError & " hid=" & HIDOverlapped.Internal

        Select Case Result
            Case WAIT_TIMEOUT
            ' Timeout error.
                Form1.lstBoxRec.AddItem "Out"
                CancelIo (ReadHandle)
                Form1.devStatus = RET_USBDEVREVTOOLOW
                DoEvents
            Case WAIT_FAILED Or WAIT_ABANDONED
                Form1.lstBoxRec.AddItem "FAIL"
                DoEvents
            Case WAIT_OBJECT_0
    '        ' Success
    '        ' Use the report data.
                rdNum = (RecBuffer(4) + 5)
                If rdNum > 65 Then rdNum = 65
              If (rdNum > 5) Then
                    For i = 1 To rdNum
                      Form1.putInCircBuff (RecBuffer(i))
                    Next i
                End If
                Form1.lstBoxRec.ListIndex = Form1.lstBoxRec.ListCount - 1
                If (rdNum > 0) Then Form1.tmrCommHndl.Enabled = True
                DoEvents
            Case Else
                Form1.lstBoxRec.AddItem "Else"
                CancelIo (ReadHandle)
                Form1.devStatus = RET_USBDEVREVTOOLOW
        End Select
        res3 = ResetEvent(EventObject)
    Loop Until res2 = 0
End Sub

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Can't tell from what you posted, the loop runs until res2=0 and res2 is not being changed in the loop so it should run forever i.e. infinite loop

What does CancelTo() do? I would suspect there is something there that is stopping it

What is this line doing

Code:

---

EventObject = CreateEvent(Security, CInt(True), CInt(False), "rdUsb")

---

?

Hi,
The issue was that the thread and the top level were all writing to the list box so eventually there would be some kind of interrupt/run-time collision