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Editorial Team
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Asked: 2026-05-23T07:26:05+00:00

I’m addapting a IR TV controller to the computer. So far I managed to

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I’m addapting a IR TV controller to the computer. So far I managed to read the controller data, map the keys and assign a great number of functions using JAVA robot class and prompt commands.

I want now to create play/pause, stop volume+ and volume – functions. Problem is it can’t be done diretly through java. I know the right way to do it is by using JNI, but I just don’t have the time to learn it right now.

The solution I found is to create exe files containing only the SendMessage function. For example, the code por the Play/Pase function would be:

#include <windows.h>

#define WM_APP_COMMAND 0x319
#define PLAY_PAUSE 0xE0000

int main() {
  SendMessage((HWND)(~0), WM_APP_COMMAND, 0, PLAY_PAUSE);
  return 0;
}

The program works, but instead of sending only one single message it keeps sending non-stop.

I have to question. The first, of course, is why the code is not working properly. Is there a break comand missing or something?.

Second is what does assigning ~0 (or 0xFFFF) to the windows handler means.

Thanks, i’m open to any kind of solution.

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1 Answer

  1. Editorial Team

    MSDN SendMesage:

    If this parameter is HWND_BROADCAST ((HWND)0xffff), the message is sent to all top-level windows in the system, including disabled or invisible unowned windows, overlapped windows, and pop-up windows; but the message is not sent to child windows.

    Broadcasting with SendMessage synchronously sends to all those windows. How this message is handled is app-dependent.

    Yes – this approach is as risky as it sounds. Can you find another way to do what you want without HWND_BROADCAST ?

    Rgds,
    Martin

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