Home > How-To Library > Internet

How to Monitor the connection to the internet

****************************************************************
*       © 2007 CodeItBetter http://www.codeitbetter.com        *
*          This notice MUST stay intact for legal use          *
****************************************************************

'Full code for monitoring connection to the internet. Includes function to be
'called by a timer which returns true or false depending on the current
'connection state.

Const RAS95_MaxEntryName = 256
Const RAS95_MaxDeviceType = 16
Const RAS95_MaxDeviceName = 32

Private Type RASCONN95
    dwSize As Long
    hRasCon As Long
    szEntryName(RAS95_MaxEntryName) As Byte
    szDeviceType(RAS95_MaxDeviceType) As Byte
    szDeviceName(RAS95_MaxDeviceName) As Byte
End Type

Private Type RASCONNSTATUS95
    dwSize As Long
    RasConnState As Long
    dwError As Long
    szDeviceType(RAS95_MaxDeviceType) As Byte
    szDeviceName(RAS95_MaxDeviceName) As Byte
End Type

Private Declare Function RasEnumConnections Lib "RasApi32.dll" Alias "RasEnumConnectionsA" _
    (lpRasCon As Any, lpcb As Long, lpcConnections As Long) As Long
Private Declare Function RasGetConnectStatus Lib "RasApi32.dll" Alias "RasGetConnectStatusA" _
    (ByVal hRasCon As Long, lpStatus As Any) As Long

'This function checks for a connection to the internet and returns true or false
'as to whether one is present
Private Function CheckInternetConnection() As Boolean
    On Error GoTo ErrHandler
    Dim TRasCon(255) As RASCONN95
    Dim lg As Long
    Dim lpcon As Long
    Dim RetVal As Long
    Dim Tstatus As RASCONNSTATUS95

    TRasCon(0).dwSize = 412
    lg = 256 * TRasCon(0).dwSize

    RetVal = RasEnumConnections(TRasCon(0), lg, lpcon)

    If RetVal <> 0 Then
        ' MsgBox "ERROR"
        Exit Function
    End If

    Tstatus.dwSize = 160

    RetVal = RasGetConnectStatus(TRasCon(0).hRasCon, Tstatus)

    If Tstatus.RasConnState = &H2000 Then
        CheckInternetConnection = True
    Else
        CheckInternetConnection = False
    End If

ExitCheckConnection:
    Exit Function

ErrHandler:
    CheckInternetConnection = False
    Resume ExitCheckConnection
End Function

'Set the timer interval to however many seconds you would like between checks * 1000
Private Sub Timer1_Timer()
    If CheckInternetConnection = True Then
        'Do whatever you need to do when connected
    Else
        'Do whatever you need to do when disconnected
    End If
End Sub

If you would like to submit your code here please us. Do not forget to mention your name. We are always thankful to each and everyone of you who submitted their code here.