Option Explicit
 
Private Declare Function InternetGetConnectedState _
        Lib "wininet.dll" (ByRef lpSFlags As Long, _
        ByVal dwReserved As Long) As Long
 
' http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wininet/wini
' net/internetgetconnectedstate.asp
Const INTERNET_CONNECTION_MODEM As Long = &H1 'Local system uses a modem to 
' connect to the Internet.
Const INTERNET_CONNECTION_LAN As Long = &H2 'Local system uses a local area 
' network to connect to the Internet.
Const INTERNET_CONNECTION_PROXY As Long = &H4 'Local system uses a proxy server 
' to connect to the Internet.
Const INTERNET_CONNECTION_MODEM_BUSY As Long = &H8 'No longer used.
Const INTERNET_CONNECTION_OFFLINE As Long = &H20 'Local system is in offline 
' mode.
Const INTERNET_CONNECTION_CONFIGURED As Long = &H40 'Local system uses a proxy 
' server to connect to the Internet.
Const INTERNET_RAS_INSTALLED As Long = &H10 'Local system has RAS installed.
 
Private Sub Out(ByVal icFlags As Long, ByVal Flag As Long, ByVal Lbl As Label)
  If Flag And icFlags Then
    Lbl.Caption = "LAN Kabel angeschlossen"
  Else
    Lbl.Caption = "LAN Kabel ab"
  End If
End Sub
 
Private Sub GetState()
    Dim icFlags As Long
    Call InternetGetConnectedState(icFlags, 0&)
    Call Out(icFlags, INTERNET_CONNECTION_LAN, Label1)
End Sub
 
Private Sub Form_Load()
    Timer1.Interval = 1000
    Timer1.Enabled = True
End Sub
 
Private Sub Timer1_Timer()
    Call GetState
End Sub