How can a Hook DLL pass data to the Process sets it .

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for example Process A(MFC Process),uses loadlibrary to load a dll and install a global hook(the hook procedure is in the dll).
I want this dll to pass any information to the Process A, So I used SendMessage in the hook procedure to send WM_COPYDATA to Process A,but it didnt work.The Process A(have setted onCopyData()) didnt receive the message , also the same as PostThreadMessage().

//Hook Procedure

C++

__declspec(dllexport)  LRESULT  CALLBACK  mousehook_proc(int nCode,WPARAM wParam,LPARAM lParam)
{	
                        COPYDATASTRUCT cds;
                        MOUSEHOOKSTRUCT *pmhs = (MOUSEHOOKSTRUCT *)lParam;
			int result = ::SendMessage((HWND)FindWindow(NULL,L"MySpyM"),WM_COPYDATA,(WPARAM)pmhs->hwnd,(LPARAM)&cds);//The MySpyM Process("MySpyM" also the Window name) did not receive the WM_COPYDATA Message and if i replace the Message with WM_CLOSE,it received.......
			return ::CallNextHookEx((HHOOK)hook_handle,nCode,wParam,lParam);
	}

//The spy program porcess the WM_COPYDATA Message

C++

BOOL CMySpyMDlg::OnCopyData(CWnd* pWnd, COPYDATASTRUCT* pCopyDataStruct)
{

	MessageBox(L"Get Message",L"Alert",NULL);
		return CDialog::OnCopyData(pWnd, pCopyDataStruct);
}

Posted 6-Feb-13 1:37am

Keanu L

Updated 6-Feb-13 12:43pm

v6

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Richard MacCutchan 6-Feb-13 9:46am

You need to provide more detail of your code, we cannot guess what is happening in your program.

Keanu L 6-Feb-13 10:40am

I want another process whose thread is installed hook to send data to the spy process using WM_COPYDATA, but the spy process coudnt receive the message....

Richard MacCutchan 6-Feb-13 10:49am

Have you traced this code to check that FindWindow() gets the correct window handle. Also how does MySpyM check for the WM_COPYDATA message? You need to show us all the information connected with this issue.

Keanu L 6-Feb-13 18:37pm

i have checked FindWindow() and it got the correct handle.i compared the handle value with the value got in Visual Studio tool Spy++.The key point is that if i replace the message with WM_CLOSE,the spy process got the message but the WM_COPYDATA.

Sergey Alexandrovich Kryukov 6-Feb-13 12:47pm

To start with, if you load a DLL using LoadLibrary, it is loaded in the calling process, not the child one.
This way, you share your address space with this DLL; and there is no problem.
Second thing: if if was not the case, exchange between the modules of different processes would be very difficult, as processes are well isolated.
Finally: you need to install a window hook in a separate DLL only if you need a global hook. Is it the case.

Probably you are mixing up processes and executable modules...
—SA

Keanu L 6-Feb-13 18:41pm

..indeed. my spy process has installed a global hook,so the another process sending message will load the dll.

Sergey Alexandrovich Kryukov 6-Feb-13 18:45pm

I don't get it. OK, if you need a global hook, install it; and you really will need a separate DLL. But it's loaded in one process, where is the other? Do you mean the processes which invoke the hooks? Then, this is the whole idea: your process has nothing to do with them, it only gets hook events...
So, what's the problem? It all depends on what do you want to do with the hook event data.
—SA

Keanu L 6-Feb-13 19:08pm

I just want the hook dll passed the hook event data to the spy process(not the sending message process) using WM_COPYDATA.
Now i have solved it. the cbData in the COPYDATASTRUCT must be set the size of the data the lpData point to.

Thank you very much~:-)

Sergey Alexandrovich Kryukov 6-Feb-13 19:11pm

Congratulations! You are welcome.
—SA

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Keanu L · Accepted Answer · 2013-02-06T13:04:00

Solution 1

I have maked a mistake. i set the COPYDATASTRUCT wrong value....
the cbData in the COPYDATASTRUCT must be set the size of the data the lpData point to.

Posted 6-Feb-13 13:04pm

Keanu L

Updated 6-Feb-13 13:09pm

v3

Comments

Richard MacCutchan 7-Feb-13 4:27am

So, in fact the receiver was getting the message, it was just not handling it well.