1. Is it possible to send a message via <dbus/dbus.h> and receive it using Qt one ?
2. Is it possible to send a message as root and receive it from app which runs on different user ? (linux)

1a. I have troubles to read the message that's why the question. This is my code:

Send <dbus/dbus.h>
Qt Code: 
  1. dbus_error_init(&_dbusError);
  2.     _dbusConnection = dbus_bus_get(DBUS_BUS_SYSTEM, &_dbusError);
  3.  
  4.     if (dbus_error_is_set(&_dbusError)) {
  5.         logger("Dbus Connection Error");
  6.         dbus_error_free(&_dbusError);
  7.         return;
  8.  
  9.     } else {
  10.         logger("Dbus Connected");
  11.     }
  12.  
  13.     _dbusMessage = dbus_message_new_signal("/", "com.app.message", "app");
  14.     if (NULL == _dbusMessage) {
  15.         logger("Message Null");
  16.         exit(1);
  17.     } else {
  18.         logger("Dbus new signal");
  19.     }
  20.  
  21.     dbus_message_iter_init_append(_dbusMessage, &_dbusMessageIter);
  22.     if (!dbus_message_iter_append_basic(&_dbusMessageIter, DBUS_TYPE_STRING, &message)) {
  23.         logger("Couldn't append dbus message");
  24.     } else {
  25.         stringstream s;
  26.         s << message;
  27.         logger("Dbus Messgae append - " + s.str());
  28.     }
  29.  
  30.     if (!dbus_connection_send(_dbusConnection, _dbusMessage, &_dbusSerial)) {
  31.         logger("Couldn't send dbus message");
  32.     } else {
  33.         logger("Dbus Messgae sent");
  34.     }
  35.  
  36.     dbus_connection_flush(_dbusConnection);
  37.     dbus_message_unref(_dbusMessage);
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Read <QtDBus/QtDBus> example from ping pong

Qt Code: 
  1. QString Pong::ping(const QString &arg)
  2. {
  3.     QMetaObject::invokeMethod(QCoreApplication::instance(), "quit");
  4.     return QString("ping(\"%1\") got called").arg(arg);
  5. }
  6.  
  7. int main(int argc, char **argv)
  8. {
  9.     QCoreApplication app(argc, argv);
  10.  
  11.     if (!QDBusConnection::sessionBus().isConnected()) {
  12.         cout << "Cannot connect to the D-Bus session bus" << endl;
  13.         return 1;
  14.     }
  15.  
  16.     if (!QDBusConnection::sessionBus().registerService("com.app.message")) {
  17.         cout << "error" << endl;
  18.         exit(1);
  19.     }
  20.  
  21.     Pong pong;
  22.     QDBusConnection::sessionBus().registerObject("/", &pong, QDBusConnection::ExportAllSlots);
  23.  
  24.  
  25.     app.exec();
  26.     return 0;
  27. }
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Thanks for looking