Checking For Blocked Ports in VB.NET

I'm currently building a program that is being used to carry out multiple checks on the computer it is running on. This includes permissions for folders & registry keys, which i have working, and checking whether ports are blocked. My issue is that i have only managed to find methods that can be used to check whether ports are open, but not blocked. Currently i use the following:

        Try
        Dim bla As TcpClient = New TcpClient("localhost", PortNumber)
        If bla.Connected = True Then
            Return True
        Else
            Return False
        End If
    Catch ex As Exception
        Return False
    End Try

Does anyone have a piece of code i can instead use to check for blocked ports?

Thanks :)`