[RESOLVED] Program hangs when closing serial port

I have a VB.Net 2008 app that I have converted from VB6 which reads data from a weight scale connected to a serial port. I am able to read the received data and display it on the screen, but when I go to Stop the reading and attempt to close the serial port, the app hangs.


Private Delegate Sub ShowWeight(ByVal tWeight As String)

Private Sub comScale_DataReceived(ByVal sender As Object, ByVal e
As System.IO.Ports.SerialDataReceivedEventArgs) Handles
comScale.DataReceived
ReadWeight(comScale.ReadLine())
End Sub

Private Sub ReadWeight(ByVal tWeight As String)
On Error GoTo ErrScale

If TextBox1.InvokeRequired Then
TextBox1.Invoke(New ShowWeight(AddressOf ReadWeight), tWeight)
Else
TextBox1.Text = tWeight
End If
strInput = TextBox1.Text
End Sub


Private Sub Command1_Click(ByVal eventSender As System.Object, ByVal
eventArgs As System.EventArgs) Handles Command1.Click
Select Case Command1(Index).Tag
Case "Stop"
RemoveHandler comScale.DataReceived, AddressOf
comScale_DataReceived
If comScale.IsOpen Then comScale.Close() 'HANGS HERE

Case "Start"
If comScale.IsOpen Then comScale.Close()
Call Get_ComPort() 'Set Port Properties
AddHandler comScale.DataReceived, AddressOf
comScale_DataReceived 'add handler
comScale.Open()
End Select
End Sub


Many Thanks for any help

Try inserting a delay between removing the handler and the comScale.Close

Code:

---

RemoveHandler comScale.DataReceived, AddressOf comScale_DataReceived
System.Threading.Thread.Sleep(1000)
If comScale.IsOpen Then comScale.Close()

---

Tried the System.Threading.Thread.Sleep(1000) as suggested but still no go.

There's an article on MSDN here http://social.msdn.microsoft.com/for...-8a4ee7b210e2/ which suggests this is a known problem A few hints but no definitive solution.

The article suggests you close the port in the FormClosing event. So if you change your program temporarily to exit before the close, and in the closing event close the port, does it still hang?

Code:

---

RemoveHandler comScale.DataReceived, AddressOf comScale_DataReceived
System.Threading.Thread.Sleep(1000)
Application.Exit

---

And in the FormClosing event

Code:

---

comScale.Close()

---

Tried placing the port close in the Form.Closed and still hangs. When I pause it the Green arrow points to the close function

Another thread here http://social.msdn.microsoft.com/For...-c562bff11a0a/ where the user appears to have overcome this.

And yet another MSDN thread suggests this;

Code:

---

RemoveHandler comScale.DataReceived, AddressOf comScale_DataReceived
Application.DoEvents()
System.Threading.Thread.Sleep(1000)
comScale.Close()

---

And one more http://social.msdn.microsoft.com/For...-5667730313ee/ suggesting a soft close method.

And another http://social.msdn.microsoft.com/For...-e2ff1d3be0a5/

All of these Ive posted seem to be resolved by the user.

p.s. Isnt MSDN great!

Changing
TextBox1.Invoke(New ShowWeight(AddressOf ReadWeight), tWeight)

to

TextBox1.BeginInvoke(New ShowWeight(AddressOf ReadWeight), tWeight)

Worked like a charm.

Thanks to all for your help. Was really stuck on this

Excellent.

In that case please mark the thread resolved.