Recently i faced lots of problem with my hosting company as almost daily my site was down due to some problems in their servers. They usually send me a link to trace my site. Basically that site provide service to ping back any URL from their servers which are located in different countries. So it is like first their US server pings the URL and sends back the results weather site is responding or not and then all of the servers located in different part of the word do the same thing and finally giving a summery. For me it was annoying to go again and again to that site and then type URL to trace it back. Furthermore they charge for their services if you wants to check your site (or any other URL) 24×7. So i decided to write my own service. In this service i write the ping back results to windows log but you can always enhance this code to send mails or even SMS if your site is down.

So lets start and create a Windows Web Service Project

Now rename your service1.vb file to PingBackSvr.vb and add another class code file to your project and name it PingBack.vb. After doing this your solution explorer should look like

Now lets start code PingBack.vb

'Namespace References
Imports System
Imports System.Runtime.InteropServices
Imports System.Net
Imports System.Net.NetworkInformation
Imports System.Net.Sockets

Public Class PingBack

<DllImport("wininet", CharSet:=CharSet.Auto)> _
Private Shared Function InternetGetConnectedState(ByRef flags As ConnectionStatusEnum, ByVal dw As Integer) As Boolean
End Function

''' <summary>
''' enum to hold the possible connection states
''' </summary>
<Flags()> _
Private Enum ConnectionStatusEnum As Integer
INTERNET_CONNECTION_MODEM = &H1
INTERNET_CONNECTION_LAN = &H2
INTERNET_CONNECTION_PROXY = &H4
INTERNET_RAS_INSTALLED = &H10
INTERNET_CONNECTION_OFFLINE = &H20
INTERNET_CONNECTION_CONFIGURED = &H40
End Enum

''' <summary>
''' method to check the status of the pinging machines internet connection
''' </summary>
''' <returns></returns>
Private Function HasConnection() As Boolean
'instance of out ConnectionStatusEnum
Dim state As ConnectionStatusEnum = 0

'call the API
InternetGetConnectedState(state, 0)

'check the status, if not offline and the returned state
'isnt 0 then we have a connection
If (CInt(ConnectionStatusEnum.INTERNET_CONNECTION_OFFLINE) And CInt(state)) <> 0 Then
'return true, we have a connection
Return False
End If
'return false, no connection available
Return True
End Function

''' <summary>
''' method for retrieving the IP address from the host provided
''' </summary>
''' <param name="host">the host we need the address for</param>
''' <returns></returns>
Private Function GetIpFromHost(ByRef host As String) As IPAddress
Dim returnMessage As String = String.Empty
'IPAddress instance for holding the returned host
Dim address As IPAddress = Nothing

'wrap the attempt in a try..catch to capture
'any exceptions that may occur
Try
'get the host IP from the name provided
address = Dns.GetHostEntry(host).AddressList(0)
Catch ex As SocketException
'some DNS error happened, return the message
returnMessage = String.Format("DNS Error: {0}", ex.Message)
End Try
Return address
End Function

''' <summary>
''' method to check the ping status of a provided host
''' </summary>
''' <param name="host">the host we need to ping</param>
''' <returns></returns>
Protected Friend Function CheckSiteStatus(ByVal host As String) As String
'string to hold our return messge
Dim returnMessage As String = String.Empty

'IPAddress instance for holding the returned host
Dim address As IPAddress = GetIpFromHost(host)

'set the ping options, TTL 128
Dim options As New PingOptions(128, True)

'create a new ping instance
Dim ping As New Ping()

'32 byte buffer
Dim data As Byte() = New Byte(31) {}

'first make sure we actually have an internet connection
If HasConnection() Then
'here we will ping the host 4 times (standard)
For i As Integer = 0 To 3
Try
'send the ping 4 times to the host and record the returned data
Dim reply As PingReply = ping.Send(address, 1000, data, options)

'make sure we dont have a null reply
If Not (reply Is Nothing) Then
Select Case reply.Status
Case IPStatus.Success
returnMessage = String.Format("Reply from {0}: bytes={1} time={2}ms TTL={3}", reply.Address, reply.Buffer.Length, reply.RoundtripTime, reply.Options.Ttl)
Exit Select
Case IPStatus.TimedOut
returnMessage = "Connection has timed out..."
Exit Select
Case Else
returnMessage = String.Format("Ping failed: {0}", reply.Status.ToString())
Exit Select
End Select
Else
returnMessage = "Connection failed for an unknown reason..."
End If
Catch ex As PingException
returnMessage = String.Format("Connection Error: {0}", ex.Message)
Catch ex As SocketException
returnMessage = String.Format("Connection Error: {0}", ex.Message)
End Try
Next
Else
returnMessage = "No Internet connection found..."
End If

'return the message
Return returnMessage
End Function
End Class

Now let’s code our Service class which in this case is PinbBackSvr.vb.

Public Class PingBackSvr
Private _objPingback As PingBack
Private _status As String
Private WithEvents timer1 As New System.Timers.Timer
Private PingLog As New EventLog
Protected Overrides Sub OnStart(ByVal args() As String)
' Add code here to start your service. This method should set things
' in motion so your service can do its work.
'Uncomment this line to Debug this service
Debugger.Launch()
timer1.Enabled = True
timer1.Interval = 6000
' Me.TracePing()
End Sub

Protected Overrides Sub OnStop()
' Add code here to perform any tear-down necessary to stop your service.
Me.Timer1.Enabled = False
End Sub

Private Sub OnTimerElapsed(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles timer1.Elapsed
Me.TracePing()
End Sub

Private Sub TracePing()
Try
If Not Diagnostics.EventLog.SourceExists("PingBackSvr") Then
Diagnostics.EventLog.CreateEventSource("PingBackSvr", "KshitijSharma.Net Ping Service Log")
End If
PingLog.Source = "PingBackSvr"
Me._objPingback = New PingBack
Me._status = Me._objPingback.CheckSiteStatus("www.kshitijsharma.net")
If InStr(Me._status, "failed") > 0 OrElse InStr(Me._status, "Error") > 0 OrElse InStr(Me._status, "timed out") > 0 Then
PingLog.WriteEntry(Me._status, EventLogEntryType.FailureAudit)
Else
PingLog.WriteEntry(Me._status, EventLogEntryType.SuccessAudit)
End If
Catch ex As Exception
PingLog.WriteEntry(ex.Message, EventLogEntryType.Error)
Finally
Me._objPingback = Nothing
PingLog = Nothing
End Try
End Sub
End Class

Now add a ‘Service Installer by right clicking design view of service.

Now Build your project

After building this service we need to install it on server.  we can do this with installUtil.exe utility. you can use

To Install
<pathofInstallUtil>\installUtil.exe /i <pathtoyourexe>

To Uninstall
<pathofInstallUtil>\installUtil.exe /u <pathtoyourexe>

Please let me know if you need help any part of this code!
Enjoy Coding!
Kshitij

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