Check network connectivity

Question

I am creating a simple application that listens to the NetworkAvailibilityChanged Event. All this is good, except for the case of connecting to the PPP interface modem, where the application receives a notification of availability only when the network is connected, but not when disconnected.

Did I miss something? I tried it for a local network and it worked perfectly.

Answer 1

Here's a touch on NetworkAvailbilityChanged.

Friend Shared Function InternalGetIsNetworkAvailable() As Boolean
    If ComNetOS.IsWinNt Then
        Dim interface2 As NetworkInterface
        For Each interface2 In SystemNetworkInterface.GetNetworkInterfaces
            If (((interface2.OperationalStatus = OperationalStatus.Up) AndAlso (interface2.NetworkInterfaceType <> NetworkInterfaceType.Tunnel)) AndAlso (interface2.NetworkInterfaceType <> NetworkInterfaceType.Loopback)) Then
                Return True
            End If
        Next
        Return False
    End If
    Dim flags As UInt32 = 0
    Return UnsafeWinINetNativeMethods.InternetGetConnectedState((flags), 0)
End Function

Private Shared Sub ChangedAddress(ByVal sender As Object, ByVal eventArgs As EventArgs)
    SyncLock AvailabilityChangeListener.syncObject
        Dim isNetworkAvailable As Boolean = SystemNetworkInterface.InternalGetIsNetworkAvailable
        If (isNetworkAvailable <> AvailabilityChangeListener.isAvailable) Then
            AvailabilityChangeListener.isAvailable = isNetworkAvailable
            Dim array As DictionaryEntry() = New DictionaryEntry(AvailabilityChangeListener.s_availabilityCallerArray.Count  - 1) {}
            AvailabilityChangeListener.s_availabilityCallerArray.CopyTo(array, 0)
            Dim i As Integer
            For i = 0 To array.Length - 1
                Dim key As NetworkAvailabilityChangedEventHandler = DirectCast(array(i).Key, NetworkAvailabilityChangedEventHandler)
                Dim context As ExecutionContext = DirectCast(array(i).Value, ExecutionContext)
                If (context Is Nothing) Then
                    key.Invoke(Nothing, New NetworkAvailabilityEventArgs(AvailabilityChangeListener.isAvailable))
                Else
                    ExecutionContext.Run(context.CreateCopy, AvailabilityChangeListener.s_RunHandlerCallback, key)
                End If
            Next i
        End If
    End SyncLock
End Sub

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