JNI -- Windows Service (Java Service Wrapper) -- Winamp

Question

Hi!
I'm developing an application to control Winamp player and this application is supposed to run as a Windows Service (via Java Service Wrapper). Winamp is
handled via JNI (c library dll).
The thing is:
When I start the application as a service, my application tries to control Winamp (eg play, pause) but it doesn't work. I can see (prints) that my application is working but all the calls of the dll that interacts with Winamp don't answer. Instead, when I stop the service, I can see finaly all the prints (I introduced in the dll play, pause functions).
Can anybody give a hand? It seems that the JNI is not working properly (in my humble opinion).
Thanks for your attention.
Best Regards
Nuno

Answer 1

In my java application:
System.out.println("Before play!");
play( ); //Native method...
System.out.println("After play!");
sleep(10*1000);
System.out.println("Before pause!");
pause ( ); //Native method...
System.out.println("After pause!");
In c file (dll lib):
JNIEXPORT void JNICALL Java_WinampController_play
(JNIEnv *env, jobject obj) {
          printf("-> cpp - Play \n");
initWinampHandle();
if (hwnd_winamp != NULL) {
SendMessageA(hwnd_winamp, WM_COMMAND, WA_PLAY,
WA_NOTHING);
          printf("<- cpp - Play \n");
JNIEXPORT void JNICALL Java_WinampController_pause
(JNIEnv *env, jobject obj) {
          printf("-> cpp - Pause \n");
initWinampHandle();
if (hwnd_winamp != NULL) {
SendMessageA(hwnd_winamp, WM_COMMAND, WA_PAUSE,
WA_NOTHING);
          printf("<- cpp - Pause \n");
Result... (log file)
Before play!
After play!
Before pause!
After pause!
And only after I stop the service, the cpp printf appear... :(
-> cpp - Play
<- cpp - Play
-> cpp - Pause
<- cpp - Pause
Thanks