Remote port scanner

Ever needed to test open ports on your machine?

Answer:
You can write a small utility for this purpose in Delphi, using sockects... here's my approach.
Use this code under you own risk, I present this article for educational purposes only, I take no responsability for the use of it.
I'll put a link to the whole demo, here's the unit, I'm sure you can recreate the form and run this:
unit PortScanU;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ScktComp;
type
TMainForm = class(TForm)
LblIPAddress: TLabel;
IPAddressE: TEdit;
lblScanRange: TLabel;
MinPortE: TEdit;
lblPorttoport: TLabel;
MaxPortE: TEdit;
StatusL: TLabel;
ActivityLB: TListBox;
StartBtn: TButton;
WSsocket: TClientSocket;
StopBtn: TButton;
OpenOnlyCB: TCheckBox;
procedure StartBtnClick(Sender: TObject);
procedure WSsocketConnect(Sender: TObject; Socket: TCustomWinSocket);
procedure WSsocketError(Sender: TObject; Socket: TCustomWinSocket;
ErrorEvent: TErrorEvent; var ErrorCode: Integer);
procedure StopBtnClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
PortX, MaxPort: Integer;
IsRunning: Boolean;
procedure SetStuffOnOff(const St: Boolean);
public
{ Public declarations }
end;
var
MainForm: TMainForm;
implementation
{$R *.dfm}
procedure TMainForm.SetStuffOnOff(const St: Boolean);
begin
IsRunning := St;
StopBtn.Enabled := St;
StartBtn.Enabled := not St;
if not (St) then
begin
ActivityLB.Items.Add('Done Scanning ' + IPAddressE.text);
StatusL.Caption := 'Status:'
end
end;
procedure TMainForm.StartBtnClick(Sender: TObject);
begin
ActivityLB.Items.Clear;
PortX := StrToInt(MinPortE.text);
MaxPort := StrToInt(MaxPortE.text);
wsSocket.Address := IPAddressE.text;
wsSocket.Port := PortX;
wsSocket.Active := True;
SetStuffOnOff(True);
ActivityLB.Items.Add('Beginning scan: ' + IPAddressE.text)
end;
procedure TMainForm.WSsocketConnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
//socket connection made
//port must be open!
ActivityLB.Items.Add('PORT: ' + inttostr(PortX) + '; OPEN!');
//try next port...
wsSocket.Active := False;
PortX := PortX + 1;
wsSocket.Port := PortX;
StatusL.Caption := 'Scanning port:[' + IntToStr(PortX) + ']';
if (IsRunning) then
if (PortX > MaxPort) then
SetStuffOnOff(False)
else
wsSocket.Active := True //test the new port
end;
procedure TMainForm.WSsocketError(Sender: TObject; Socket: TCustomWinSocket;
ErrorEvent: TErrorEvent; var ErrorCode: Integer);
begin
//connection failed....
ErrorCode := 0; //handle the error
if not (OpenOnlyCB.Checked) then
ActivityLB.Items.Add('Port: ' + inttostr(PortX) + '; Closed.');
//try next port
wsSocket.Active := False; //close it
PortX := PortX + 1; //new port to check
wsSocket.Port := PortX; //put the port in the socket
StatusL.Caption := 'Scanning port:[' + IntToStr(PortX) + ']';
if (IsRunning) then
if (PortX > MaxPort) then
SetStuffOnOff(False)
else
wsSocket.Active := True //test the new port
end;
procedure TMainForm.StopBtnClick(Sender: TObject);
begin
SetStuffOnOff(False);
wssocket.Active := False;
ActivityLB.Items.Add('Stoped scan; port ' + inttostr(PortX) + '!')
end;
procedure TMainForm.FormCreate(Sender: TObject);
begin
IsRunning := False
end;
end.

as you can see, the idea is pretty easy...

set the address
set the port
try to activate the socket
and check if it went good
next port, repeat steps

note:to test ports on your local machine you need to set IPAddressE.Text:='localhost'

Author: Eber Irigoyen
Product: Delphi 2.x (or higher)