Obtain the list of open ports, windows firewall - arrays

Question

I am trying to develop a code that manages the firewall ports using vb.net. The first part is to list all ports enabled. so I am trying this code:
Function portsList()
Dim ports As INetFwOpenPorts
Dim port As INetFwOpenPort
Dim myPorts() As INetFwOpenPorts
Dim NetFwMgrType As Type = Type.GetTypeFromProgID("HNetCfg.FwMgr", False)
Dim mgr As INetFwMgr = DirectCast(Activator.CreateInstance(NetFwMgrType), INetFwMgr)
ports = DirectCast(mgr.LocalPolicy.CurrentProfile.GloballyOpenPorts, INetFwOpenPorts)
Dim enumerate As System.Collections.IEnumerator = ports.GetEnumerator()
Dim i As Integer
While enumerate.MoveNext()
port = DirectCast(enumerate.Current, INetFwOpenPort)
myPorts(i) = port
i += 1
End While
Dim portAsString() As String
For j As Integer = 0 To i
portAsString(j) = myPorts(j).ToString
Next
Return portAsString
End Function
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Dim ports() As String = portsList()
Dim n As String = ports.Length
Dim newString As String = ""
For h As Integer = 0 To n
newString = ports(h) & vbNewLine
Next
RichTextBox1.Text = newString
End Sub
What I want to do is list all the ports in Richtextbox1 after clicking Button4. The error that I am getting is:
NullReferenceException was unHandled. Object reference not set to an instance of an object.
I am new to Vb, how can I get over this?

Answer 1

Try this:
For port As Integer = 1 to maxPorts
Dim host As String = "192.168.1.7"
Dim hostadd As Net.IPAddress = Net.Dns.GetHostEntry(host).AddressList(0)
Dim EPhost As New Net.IPEndPoint(hostadd, port)
Dim s As New Net.Sockets.Socket(Net.Sockets.AddressFamily.InterNetwork, Net.Sockets.SocketType.Stream, Net.Sockets.ProtocolType.Tcp)
Try
s.Connect(EPhost)
Catch
End Try
If s.Connected Then
'Port opened
Else
'Port closed
End If
Next
Here you have the complete project.