.NET [tut] creating a TCP port scanner in Visual Basic.net

[.NET] [tut] creating a TCP port scanner in Visual Basic.net - Printable Version

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[tut] creating a TCP port scanner in Visual Basic.net - ***** - Apr 18, 2011

Today i will demonstrate how to create your own port scanner in Visual basic.net

Basically, it will preform the same function as n-map (albeit with much less features)

How will this work?
Basically, this port scanner will try to create a TCP connection to every port within the specified port range. If the connection can be successfully established, than the port will be listed as open, if the connection cannot be opened, than the port will be listed as closed.

Basically, this is how every port scanner works. However, better port scanners like n-map can scan using more methods than just attempting to establish a tcp connection. fur example the syn scan.

unfortunately, this port scanner will list every port that it cannot establish a connection with as "closed". this might not be accurate, as there can be many reasons why a connection cannot be established.

creating the port scanner
first of all, create a new console application, and delete all the code

import the required stuff:

Code 
Imports System.Net.Sockets

Imports System.Net

Imports System.Threading

Imports System.Text

these imports will allow us to use many much needed methods, like Tcpconnect()

now the class:

Code 
Public Class psAPP

    Public Shared Sub Main()

    End Sub

End Class

and declare the variables

Code 
Dim portStart As Integer

  Dim portEnd As Integer

  Dim lngPort As Long

  Dim txtHost As String

  Dim openPorts As Integer

  Dim closedPorts As Integer

the user imput:

Code 
Console.Write("Host: ")

  txtHost = Console.ReadLine()

  Console.Write("From: ")

  portStart = Console.ReadLine()

  Console.Write("To: ")

  portEnd = Console.ReadLine()

this is to determine the host to scan , and the range of ports to scan

scanning the host:

Code 
For lngPort = portStart To portEnd

    Dim myTcpClient As New TcpClient()

    Try

    myTcpClient.Connect(txtHost, lngPort)

    Console.WriteLine("Host: " + txtHost + " : ")

    Console.WriteLine("  Port " + lngPort.ToString() + " : Open :")

    openPorts += 1

    myTcpClient.Close()

    Catch ex As SocketException

    Console.WriteLine("Host: " + txtHost + " : ")

    Console.WriteLine("  Port " + lngPort.ToString() + " : Closed :")

    ' Console.WriteLine(ex.Message)

    closedPorts += 1

    End Try

  Next

this works by trying to connect to every port within the scan range, and see if a connection can be established or not

output code:

Code 
Console.Write("    " & openPorts.ToString & " open port(s) : ")

  Console.Write("     " & closedPorts.ToString & " closed port(s) : ")

  Console.Beep()

  Console.Write(txtHost + " : " + portStart.ToString + " - " + portEnd.ToString + " : Scanned Sucessfully")

this is the final code that displays the out come to the user
example code

Code 
Imports System.Net.Sockets

Imports System.Net

Imports System.Threading

Imports System.Text

Public Class Tester

    Public Shared Sub Main()

  Dim portStart As Integer

  Dim portEnd As Integer

  Dim lngPort As Long

  Dim txtHost As String

  Dim openPorts As Integer

  Dim closedPorts As Integer

  Console.Write("Host: ")

  Console.Write("")

  txtHost = Console.ReadLine()

  Console.Write("From: ")

  Console.Write("")

  portStart = Console.ReadLine()

  Console.Write("To: ")

  Console.Write("")

  portEnd = Console.ReadLine()

  Console.WriteLine("")

  For lngPort = portStart To portEnd

    Dim myTcpClient As New TcpClient()

    Try

    myTcpClient.Connect(txtHost, lngPort)

    Console.WriteLine("Host: " + txtHost + " : ")

    Console.WriteLine("  Port " + lngPort.ToString() + " : Open :")

    openPorts += 1

    myTcpClient.Close()

    Catch ex As SocketException

    Console.WriteLine("Host: " + txtHost + " : ")

    Console.WriteLine("  Port " + lngPort.ToString() + " : Closed :")

    ' Console.WriteLine(ex.Message)

    closedPorts += 1

    End Try

  Next

  Console.WriteLine("")

  Console.Write("    " & openPorts.ToString & " open port(s) : ")

  Console.Write("     " & closedPorts.ToString & " closed port(s) : ")

  Console.WriteLine("" & vbCrLf)

  Console.Beep()

  Console.Write(txtHost + " : " + portStart.ToString + " - " + portEnd.ToString + " : Scanned Sucessfully")

  Console.ReadLine()

    End Sub

End Class"

and now we are done🤗

* - SoulZeh - Apr 18, 2011

Post a Screen Shot pleasee
but nice tut <3

* - ***** - Apr 18, 2011

(Apr 18, 2011 07:49 PM)KevvYE Wrote: Post a Screen Shot pleasee
but nice tut <3

the result (not created by me though):
[img]http://img38.imageshack.us/img38/6430/finishedporj.png[/img]

* - Arjun21 - Oct 18, 2011

Very nice tutorial man..
Thanks..
Keep posting