Question

Windows Interprocess communication.

WM_CopyData IPC (data copy) - source code (c++)

windows data copy IPC code

Answer 1

Windows WM_COPYDATA message will be used to send data to another process. Every windows message has two parameters – WPARAM and LPARAM. One needs to set both follows:

WPARAM: A handle to window passing the data
LPARAM: A pointer to a COPYDATASTRUCT structure that contains the data to be passed.

Source code(C++)

SendMessage(hwnd, // Handle to destination window
WM_COPYDATA, // Message to send to destination window
(WPARAM)wparam, // Handle to window passing the data
(LPARAM)lparam); // Data (pointer to COPYDATASTRUCT)

CString sMsg(_T("Hello this message is from WM_COPYDATA"));
COPYDATASTRUCT data;
data.dwData = 1;
data.cbData = sMsg.GetLength()*sizeof(WCHAR);
data.lpData = &sMsg;

HWND destWnd = FindWindow(_T("WinClassName"), _T("WindowName"));
SendMessage(destWnd, WM_COPYDATA, (WPARAM)(HWND)hwnd, (LPARAM)(LPVOID)&data);

The receiving application should implement the WM_COPYDATA message in its message loop and would retrieve as follows:

case WM_COPYDATA:
PCOPYDATASTRUCT pcData;
pcData = (PCOPYDATASTRUCT) lParam;
CString* sRecvMsg = pcData->lpData;
break;