Interrupting loop in VB.net - vb.net

Question

I have a loop that runs but would like it to stop on the press of a button and start again when another is pressed. This is my code:
Public Class Form1
Private loopon As Boolean
Public Function ping(ByVal server As String) As String
Dim s As New Stopwatch
s.Start()
My.Computer.Network.Ping(server)
s.Stop()
Return s.ElapsedMilliseconds.ToString
End Function
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
loopon = True
TextBox1.Text = "Ping results:"
Do While loopon = True
TextBox1.AppendText(Environment.NewLine)
TextBox1.AppendText(ping("server name here"))
Loop
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
loopon = False
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TextBox1.Text = String.Empty
TextBox1.Text = "Ping results:"
loopon = True
End Sub
End Class
When I try to run the code, with debugging, my computer gives me a blue screen after a while and restarts. I'm pretty sure I messed up with the exiting of the loop. Any suggestions?

Answer 1

You could use a Timer to ping (say) every 5 seconds until the "Stop" button is clicked. In the Form Designer, drag a Timer onto the form, and use this code:
Public Class Form1
Private stopPing As Boolean
Public Sub Ping(ByVal server As String)
Dim s As New Stopwatch
s.Start()
My.Computer.Network.Ping(server)
s.Stop()
TextBox1.AppendText(Environment.NewLine & s.ElapsedMilliseconds.ToString)
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
TextBox1.Text = "Ping results:"
Ping "server name here"
Timer1.Interval = 5000 'Set timer Interval to 5 seconds
Timer1.Start
End Sub
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
stopPing = True
End Sub
Sub Timer1_Tick(sender As Object, e As EventArgs) Handles Timer1.Tick
If stopPing Then Timer1.Stop Else Ping "server name here"
End Sub
End Class