'Überprüft die Verfügbarkeit einer Netzwerkadresse (IP, Port)
    Private Function checkNetworkAddress(ByVal ip As String, ByVal port As _
      String) As Boolean
        Dim check As Boolean
        Dim ns As System.Net.Sockets.NetworkStream
        Dim bytes As Byte()
        Dim theServer As System.Net.Sockets.TcpClient
 
        check = True
 
        Try
            theServer = New System.Net.Sockets.TcpClient(ip, port)
            bytes = System.Text.Encoding.ASCII.GetBytes("Ping")
            ns = theServer.GetStream()
            ns.Write(bytes, 0, bytes.Length)
            theServer.Close()
            ns.Close()
        Catch ex As Exception
            check = False
        End Try
 
        Return check
    End Function