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how to use vb.net to check if my winform application is block by firewall TCP/port

Posted on 2011-03-25
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Last Modified: 2012-06-21
Hi
I want winform application to be aware of firewall that would block TCP and Port it is using.

Is there such code? to check if firewall is blocking?
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Question by:JSW21
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Accepted Solution

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Hairbrush earned 2000 total points
ID: 35213960
Hi

Yes, it is possible to do this.  You will need to use the System.Net.Sockets namespace in the .NET Framework.  Try the code below:
Dim hostname As String = "server1"
Dim portno As Integer = 9081
Dim ipa As IPAddress = CType(Dns.GetHostAddresses(hostname)(0), IPAddress)
Try
	Dim sock As System.Net.Sockets.Socket = New System.Net.Sockets.Socket(System.Net.Sockets.AddressFamily.InterNetwork, System.Net.Sockets.SocketType.Stream, System.Net.Sockets.ProtocolType.Tcp)
	sock.Connect(ipa, portno)
	If sock.Connected = True Then ' Port is in use and connection is successful
			MessageBox.Show("Port is Closed")
	End If
	sock.Close()

Catch ex As System.Net.Sockets.SocketException
	If ex.ErrorCode = 10061 Then ' Port is unused and could not establish connection
		MessageBox.Show("Port is Open!")
	Else
		MessageBox.Show(ex.Message)
	End If
End Try

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Author Closing Comment

by:JSW21
ID: 35217934
sock.close
will allow me to really connect it again later right?
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LVL 12

Expert Comment

by:Hairbrush
ID: 35230399
Yes.
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