Carrying Out Commands in a Server Application

A Win32-based application can use the WM_DDE_EXECUTE message to cause a certain command or series of commands to be carried out in another application. To do this, the client sends the server a WM_DDE_EXECUTE message containing a handle to a command string, as shown in the following example.

if (!(hCommand = GlobalAlloc(GMEM_MOVEABLE | GMEM_DDESHARE,

sizeof(szCommandString) + 1)))

return;

if (!(lpCommand = GlobalLock(hCommand))) {

GlobalFree(hCommand);

return;

}

lstrcpy(lpCommand, szCommandString);

GlobalUnlock(hCommand);

if (!PostMessage(hwndServerDDE,

WM_DDE_EXECUTE,

(WPARAM) hwndClientDDE,

PackDDElParam(WM_DDE_EXECUTE, 0, (UINT) hCommand))) {

GlobalFree(hCommand);

FreeDDElParam(WM_DDE_EXECUTE, lParam);

}

In this example, the server attempts to carry out the specified command string. If it succeeds, the server sends the client a positive WM_DDE_ACK message; otherwise, it sends a negative WM_DDE_ACK message. This WM_DDE_ACK message reuses the hCommand handle passed in the original WM_DDE_EXECUTE message.

If the client's command execution string requests that the server terminate, the server should respond by sending a positive WM_DDE_ACK message and then post a WM_DDE_TERMINATE message before terminating. All other commands sent with a WM_DDE_EXECUTE message should be executed synchronously; that is, the server should send a WM_DDE_ACK message only after successfully completing the command.

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