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Cant connect but dont get an error [message #39500]

Sat, 23 March 2013 16:03

Brat
Messages: 7
Registered: March 2013

Promising Member

Hello,
sorry for my bad english, i'm from germany.

I want to check whether a port is open or not.

Here is my code:

main.cpp

#include "PortScan.h"
using namespace Upp;
PortScan::PortScan() {
	CtrlLayout(*this, "Simple Portscanner");
	InBtnScan <<= THISBACK(Button);
}

void PortScan::Button(){
	int sPort 	= InStartPort;
	int ePort 	= InEndPort;
	String url 	= InStrUrl;
	TcpSocket socket;
	
	
	socket.Connect(url, sPort);
	socket.Timeout(200);
	
	if(!socket.IsError()){
		PromptOK("Port is open");
	}
	
	socket.Close();
}

GUI_APP_MAIN {
	PortScan().Run();
}

PortScan.h

#ifndef _PortScan_PortScan_h
#define _PortScan_PortScan_h

#include <CtrlLib/CtrlLib.h>

using namespace Upp;

#define LAYOUTFILE <PortScan/PortScan.lay>
#include <CtrlCore/lay.h>

class PortScan : public WithPortScanLayout<TopWindow> {
	public:
		typedef PortScan CLASSNAME;
		PortScan();
		void Button();
};

#endif

PortScan.lay

LAYOUT(PortScanLayout, 524, 152)
	ITEM(EditInt, InStartPort, HSizePosZ(68, 212).TopPosZ(80, 19))
	ITEM(EditInt, InEndPort, LeftPosZ(68, 244).TopPosZ(104, 19))
	ITEM(EditString, InStrUrl, LeftPosZ(68, 244).TopPosZ(56, 19))
	ITEM(Label, dv___3, SetLabel(t_("URL")).LeftPosZ(4, 56).TopPosZ(56, 20))
	ITEM(Label, dv___4, SetLabel(t_("Start Port")).LeftPosZ(4, 56).TopPosZ(80, 20))
	ITEM(Label, dv___5, SetLabel(t_("End Port")).LeftPosZ(4, 56).TopPosZ(104, 20))
	ITEM(Button, InBtnScan, SetLabel(t_("Scan")).LeftPosZ(4, 56).TopPosZ(132, 15))
END_LAYOUT

The URL Input field defines the host, Start Port defines the Port to check. End Port isnt used yet (Want to create a simple Portscanner).

I compiled and tested my program under OpenSuSE 12.1
uname -a:

Linux linux-m3d8.site 3.1.10-1.16-desktop #1 SMP PREEMPT Wed Jun 27 05:21:40 UTC 2012 (d016078) x86_64 x86_64 x86_64 GNU/Linux

The program compiles without an error, but it says every port on every host is open. How can i change this? I allready tryed to use "if(socket.IsOpen())" - but this didnt change anything.

[Updated on: Sat, 23 March 2013 16:04]

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Re: Cant connect but dont get an error [message #39560 is a reply to message #39500]

Sat, 30 March 2013 09:47

mirek
Messages: 13975
Registered: November 2005

Ultimate Member

This is a bit more tricky than it seems - socket API (I mean, Linux/Win32, not U++ encapsulation) is highly optimized and queued, for example Connect just starts connection to the port, without actually finishing it - and OS might detect that to connection is not available a couple of operations later.

Anyway, I have tried and this seems to work:

	TcpSocket socket;
	for(int i = 1; i < 120; i++)
		LOG(i << ' ' << (socket.Timeout(2000).Connect(url, i) && socket.Wait(WAIT_WRITE) && socket.Put("\n") == 1));

Please note that scanning ports is generally considered as form of attack...

Mirek

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