Ping machines from list and update .txt file

Imports System.Net
Imports System.Net.NetworkInformation
Imports System.ComponentModel
 
Public Class Form1
 
    Private p As New Ping
    Private WithEvents workers As New List(Of BackgroundWorker)
    Private sets As New List(Of PingTest)
    Private hosts As New Hashtable
    Private cancel As Boolean = True
 
    Private Function PingIt(ByVal host As String) As PingReply
        Return p.Send(host)
    End Function
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim ofd As New OpenFileDialog
        ofd.Filter = "Text Files (*.txt)|*.txt"
        If ofd.ShowDialog = Windows.Forms.DialogResult.OK Then
            If ofd.FileName.Length > 0 Then
                If ofd.FileName.EndsWith(".txt") Then
                    TextBox1.Text = ofd.FileName
                End If
            End If
        End If
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Label3.Text = Now.ToString
        Button2.Enabled = False
        Button3.Enabled = Not Button2.Enabled
        cancel = False
        workers.Clear()
        sets.Clear()
        hosts.Clear()
        Try
            Dim hs() As String = System.IO.File.ReadAllText(TextBox1.Text).Split(vbLf)
            For h As Integer = 0 To hs.Length - 1
                If hs(h).Trim.Length > 0 Then
                    hosts.Add(h, hs(h).Trim)
                    workers.Add(New BackgroundWorker())
                    sets.Add(New PingTest)
                    AddHandler workers(h).DoWork, AddressOf DoJob
                    workers(h).RunWorkerAsync(New Object() {h})
                End If
            Next
        Catch ex As Exception
            MsgBox(ex.Message)
            Button2.Enabled = True
            Button3.Enabled = Not Button2.Enabled
        End Try
    End Sub
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        cancel = True
        Button2.Enabled = True
        Button3.Enabled = Not Button2.Enabled
    End Sub
 
    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        For s As Integer = 0 To sets.Count - 1
            sets(s).WriteXml(My.Application.Info.DirectoryPath & "\" & hosts(s) & ".xml")
        Next
        MsgBox("Exported")
    End Sub
 
    Private Sub DoJob(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
        While Not cancel
            Dim rep As PingReply = PingIt(hosts(e.Argument(0)))
            sets(e.Argument(0)).Pings.AddPingsRow(Now, hosts(e.Argument(0)), rep.RoundtripTime, rep.Status = IPStatus.Success)
            System.Threading.Thread.Sleep(NumericUpDown1.Value)
        End While
    End Sub
 
 
 
End Class

                                              

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