Ping A System from vb.Net

Network ping is a quick way to check to see if a remote system is online (assuming the remote system does not have ping response blocked). There are basically two steps involved in this example: First, make sure that we are able to resolve the hostname to an IP address; if we can't do that, there's no point in attempting to ping it. Once we are able to resolve the hostname's IP address, we can move on to second step which is the actual ping operation. This is relatively simple in .Net Framework (2.0) using vb.Net.

Environment: VB.NET, Visual Studio 2005, .NET 2.0

STEP ONE:
Create a Windows Form application and place the following three controls on it.

(1) A TextBox control
- change the name to "txtHostName"
(2) A Button conrol
- change the name to "btnPingHost"
(3) A second TextBox Control
- change the name to "txtPingResult"
- set the "Multiline" property to "True"
- make the control big enough to show the ping output,
approximately 400(width) by 200(height)

STEP TWO:
Paste the following code into the "codebehind" for this form.

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Imports System.Net.NetworkInformation
Imports system.net
Imports System.Threading
Imports System.Text

Public Class Form1

Private Sub btnPingHost_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnPingHost.Click
  If HostIsResolvable(txtHostName.Text) Then
      PingSystem(txtHostName.Text)
  End If
End Sub

Sub PingSystem(ByVal HostName As String)
  'Ping the system and display results to the txtPingResult control

  'Clear any previous ping results
  txtPingResult.Text = ""

  Dim pingsender As New Ping
  Dim options As New PingOptions

  'Modify the default fragmentation behavior
  options.DontFragment = True

  'Create a buffer of 32 bytes of data to be transmitted.      
  Dim data As String = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
  Dim buffer As Byte() = Encoding.ASCII.GetBytes(data)
  Dim timeout As Integer = 120

  Try
      'Attempt ping
      Dim reply As PingReply = pingsender.Send(HostName, timeout, buffer, options)
      'Ping the target system 4 times to check for consistent results
      For i As Integer = 1 To 4
          If (reply.Status = IPStatus.Success) Then
              txtPingResult.Text += String.Format("Reply from:{1}: Bytes={2} time{3} TTL={4}{0}", _
                  vbCrLf, reply.Address.ToString, reply.Buffer.Length, GetMs(reply.RoundtripTime), reply.Options.Ttl)
          Else
              txtPingResult.Text += String.Format("Ping Failed:{1}{0}", vbCrLf, reply.Status.ToString)
          End If
          Me.Refresh()
          'Pause for 1 second before pinging again
          System.Threading.Thread.Sleep(1000)
      Next
  Catch ex As Exception
      txtPingResult.Text += String.Format("Ping Failed on host:{1}{0}Error:{2}{0}Detail:{3}{0}", vbCrLf, HostName, ex.Message, ex.InnerException)
  End Try
  txtPingResult.Text += "-- done --"
End Sub

Function HostIsResolvable(ByVal HostName As String) As Boolean
  'Attempt to lookup hostname in DNS
  'If successful, simply return TRUE
  'If not successful, Return FALSE and display message to txPingResult control
  Try
      'performs the DNS lookup
      Dim HostEntry As IPHostEntry = Dns.GetHostEntry(HostName)
      Dim IpList As IPAddress() = HostEntry.AddressList
      HostIsResolvable = True
  Catch ex As System.Exception
      txtPingResult.Text = ex.Message
      HostIsResolvable = False
  End Try

End Function

Function GetMs(ByVal ResponseTime As Integer) As String
  'accept and integer value and return a friendly string
  '  reflecting number of milliseconds
  If ResponseTime = 0 Then
      Return "<1ms">
  Else
      Return String.Format("={0}ms", ResponseTime.ToString)
  End If
End Function

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