Inter-Process Communication (IPC) Introduction and Sample Code

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    WIN32 APPLICATION : CppReceiveWM_COPYDATA Project Overview
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Use:

IPC based on the Windows message WM_COPYDATA is a mechanism for exchanging 
data among Windows applications in the local machine. The receiving 
application must be a Windows application. The data being passed must not 
contain pointers or other references to objects not accessible to the 
application receiving the data. While WM_COPYDATA is being sent, the 
referenced data must not be changed by another thread of the sending process. 
The receiving application should consider the data read-only. The lParam 
parameter is valid only during the processing of the message. The receiving 
application should not free the memory referenced by lParam. If the receiving 
application must access the data after SendMessage returns, it needs to copy 
the data into a local buffer.

CppReceiveWM_COPYDATA demonstrates how a receiving process handles the 
WM_COPYDATA message to get the passed data.


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Project Relation:

CppSendWM_COPYDATA -> CppReceiveWM_COPYDATA
CppSendWM_COPYDATA sends data to CppReceiveWM_COPYDATA through the  
WM_COPYDATA message.


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Code Logic:

1. In DiagProc or WndProc, capture and handle the WM_COPYDATA message

	HANDLE_MSG (hWnd, WM_COPYDATA, OnCopyData);
	
	BOOL OnCopyData(HWND hWnd, HWND hwndFrom, PCOPYDATASTRUCT pcds)
	{  }

2. Get the COPYDATASTRUCT struct from Lparam of the WM_COPYDATA message, and 
fetch the data (MyStruct object) from COPYDATASTRUCT.lpData.

	MyStruct myStruct;
	memcpy(&myStruct, pcds->lpData, sizeof(MyStruct));

4. Display the data in the form.


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References:

MSDN: WM_COPYDATA Message
http://msdn.microsoft.com/en-us/library/ms649011.aspx

MSDN: Using Data Copy
http://msdn.microsoft.com/en-us/library/ms649009.aspx

Inter Process Communication using WM_COPYDATA
http://www.codersource.net/mfc_ipc_wm_copydata.aspx


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