Checking Internet Connection

The Microsoft WinINet API enables applications to access standard Internet protocols, such as FTP and HTTP.

Many of you want to know if a computer has an active Internet connection before trying to connect to the internet using some communication interface. We can determine it by using one of WinINet function for check the status of internet connection in a computer.

  Private Declare Function InternetGetConnectedState Lib "wininet" _
  (ByRef conn As Long, ByVal val As Long) As Boolean

InternetGetConnectedState function retrieves the connected state of the local system. A return value of TRUE from InternetGetConnectedState indicates that at least one connection to the Internet is available.

Imports System.Runtime.InteropServices

Public Class Form1
   Private Declare Function InternetGetConnectedState Lib "wininet" (ByRef conn As Long, ByVal val As Long) As Boolean

   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
      Dim Out As Integer
      If InternetGetConnectedState(Out, 0) = True Then
          MsgBox("Connected !")
      Else
          MsgBox("Not Connected !")
      End If
   End Sub
End Class

Souce From : http://net-informations.com/vbprj/communications/internet-connection.htm