Adding Port to Ping

Question

I am using VB.net to ping a domain/IP, using the following code;

My.Computer.Network.Ping(Address, 1000)

I now want to add a port to the domain/IP - e.g google.co.uk:21

How would I go about this?

Answer 1

You cannot ping a port but you can try to connect to a specific port using either TCP/IP or UDP. The port concept belongs to the transport layer of the protocol stack (either TCP or UDP) while the ping is at the lower network layer (the ICMP protocol).

Answer 2

You can test if a port is "open" by using this function:

Function CheckPortOpen(ByVal hostname As String, ByVal portnum As Integer) As Boolean

    Dim ipa As IPAddress = CType(Dns.GetHostAddresses(hostname)(0), IPAddress)

    Try
        Dim sock As Socket = New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
        Console.WriteLine("Testing " & hostname & ":" & portnum)
        sock.Connect(ipa, portnum)
        If (sock.Connected = True) Then
            sock.Close()
            sock = Nothing
            Return True
       End If

    Catch sx As SocketException
        If sx.ErrorCode = 10061 Then
            Return False
        Else
            Return Nothing
        End If

    End Try

End Function