Global keyboard Hook not working

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I have been trying to make Global Keyboard hook program in visual C++ that writes keystrokes to a file "log.txt"..I am new to windows programming and i have gone through the msdn library to get an understanding of hooks....I think i have understood the concept theoretically but when i implement the code, it doesn't seem towork..The compiler doesn't show any error in both the DLL file and EXE file....Moreover the text file "log.txt" never gets created...
Here are the code files

First the DLL file:

C++

#include <windows.h>
#include <stdio.h>

HHOOK g_hhk;

__declspec(dllexport) LRESULT CALLBACK KeyProc(int nCode, WPARAM wParam, LPARAM lParam)
{
	if(nCode>=0)
	{
		char ch;
		FILE *fp;
		fp=fopen("log.txt","a");
	if((wParam==VK_SPACE)||(wParam==VK_RETURN)||(wParam>=0x2f ) &&(wParam<=0x100))
	{
	if(wParam==VK_RETURN)
		ch='\n';
		fwrite(&ch,1,1,fp);
	}
	else
	{
		BYTE ks[256];
		GetKeyboardState(ks);

		WORD w;

		UINT scan;

		scan=0;

		ToAscii(wParam,scan,ks,&w,0);

		ch =char(w);

        fwrite(&ch,1,1,fp);  // copy character to log file
	}
	fclose(fp);
	}
return CallNextHookEx(g_hhk, nCode, wParam, lParam);
}

Now the EXE file:

C++

#include <windows.h>

HOOKPROC hkprckb;
static HINSTANCE hinstDLL; 
static HHOOK hhookkb;

int WINAPI WinMain(HINSTANCE hInstance1,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nShowCmd)
{
	hinstDLL=LoadLibrary(TEXT("C:\\Documents and Settings\\Attar Singh\\My Documents\\Visual Studio 2008\\Projects\\key\\Debug\\key.dll"));
	hkprckb=(HOOKPROC)GetProcAddress(hinstDLL,"KeyProc");
	hhookkb=SetWindowsHookEx( 
                    WH_KEYBOARD_LL,
                    hkprckb,
                    hinstDLL,
                    0); 


	
	MessageBox(NULL,NULL,NULL,MB_OK);
	return 1;
}

This program is giving me nightmares...Any sort of help will be greatly appreciated...thanks in advance...!!

Posted 30-Jul-11 2:08am

ravi_2105

Updated 30-Jul-11 2:14am

Richard MacCutchan

v2

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«_Superman_» · Answer 1 · 2011-07-30T06:38:00

Solution 1

You need to store the HHOOK variable in a shared data segment.
Create it using the #data_seg directive.
Take a look at my article - Mousey! Roll Over and Park[^]

Posted 30-Jul-11 6:38am

«_Superman_»

mbue · Answer 2 · 2011-07-31T14:20:00

Try this:

////////////////////
// DLL

HHOOK        __hhook = 0;

LRESULT FAR PASCAL KeyProc(int nCode, WPARAM wParam, LPARAM lParam)
{
  // do the things you want
  return CallNextHookEx(__hhook,nCode,wParam,lParam);
}

int FAR PASCAL DllMain(HANDLE hModule,unsigned long r,void* p)
{
  switch(r)
  {
    case DLL_PROCESS_ATTACH:
      __hhook = SetWindowsHookEx( WH_KEYBOARD_LL,KeyProc,hModule,0); 
    break;
    case DLL_PROCESS_DETACH:
      UnhookWindowsHookEx(__hhook);
    break;
    case DLL_THREAD_ATTACH: break;
    case DLL_THREAD_DETACH: break;
  }
  return 1;
}



////////////////////
// EXE
int FAR PASCAL WinMain(HINSTANCE h,HINSTANCE p,LPSTR c,int sw)
{
  HINSTANCE  hdll = LoadLibrary(TEXT("key.dll"));
  MessageBox(0,__TEXT("wait..."),__TEXT("keyhook"),MB_OK);
  FreeLibrary(hdll);
  return 1;
}

You have nothing to export only load the DLL. The function is injected to every process and DllMain is called. But remember the hook will stay until windows shut down. Otherwise you should send a signal (i.e. an event object or a special keystoke) to unkook and terminate.
Good luck.