Как я могу сделать disconnect от Интернета, используя VisualBasic?

Если Вам нужно завершить все соединения с интернетом используя Visual Basic, Вы можете использовать функции Remote Access Services Hangup. Перво наперво необходимо объявить следующий код в секции declaration формы или модуля.

Declarations

Public Const RAS_MAXENTRYNAME As Integer = 256
Public Const RAS_MAXDEVICETYPE As Integer = 16
Public Const RAS_MAXDEVICENAME As Integer = 128
Public Const RAS_RASCONNSIZE As Integer = 412
Public Const ERROR_SUCCESS = 0&

Public Type RasEntryName
    dwSize As Long
    szEntryName(RAS_MAXENTRYNAME) As Byte
End Type

Public Type RasConn
    dwSize As Long
    hRasConn As Long
    szEntryName(RAS_MAXENTRYNAME) As Byte
    szDeviceType(RAS_MAXDEVICETYPE) As Byte
    szDeviceName(RAS_MAXDEVICENAME) As Byte
End Type

Public Declare Function RasEnumConnections Lib _
"rasapi32.dll" Alias "RasEnumConnectionsA" (lpRasConn As _
Any, lpcb As Long, lpcConnections As Long) As Long

Public Declare Function RasHangUp Lib "rasapi32.dll" Alias _
"RasHangUpA" (ByVal hRasConn As Long) As LongPublic _
gstrISPName As String

Public ReturnCode As Long

Procedure

Public Sub HangUp()
Dim i As Long
Dim lpRasConn(255) As RasConn
Dim lpcb As Long
Dim lpcConnections As Long
Dim hRasConn As Long
lpRasConn(0).dwSize = RAS_RASCONNSIZE
lpcb = RAS_MAXENTRYNAME * lpRasConn(0).dwSize
lpcConnections = 0
ReturnCode = RasEnumConnections(lpRasConn(0), lpcb, _
lpcConnections)

If ReturnCode = ERROR_SUCCESS Then
    For i = 0 To lpcConnections - 1
        If Trim(ByteToString(lpRasConn(i).szEntryName)) _
            = Trim(gstrISPName) Then
            hRasConn = lpRasConn(i).hRasConn
            ReturnCode = RasHangUp(ByVal hRasConn)
        End If
    Next i
End If

End Sub

Public Function ByteToString(bytString() As Byte) As String
Dim i As Integer
ByteToString = ""
i = 0
While bytString(i) = 0&
ByteToString = ByteToString & Chr(bytString(i))
i = i + 1
Wend
End Function

Использование процедуры HangUp

теперь достаточно просто вызвать процедуру HangUp, и все модемные соединия завершаться:

Call HangUp