Can't send control message

[Wnt2bsleepin]

I am new to USB and am trying to communicate with a dongle. So far, the only endpoint that is showing is 0x81, which is apparently an in only. I am trying to send it a status request.

byte[] data= new byte[]{0,0,0,0}; 
        //Data to read from device
        byte[] readData = new byte[data.length];

        dev.open(1, 0, 0);
        int altInterface = dev.getAltinterface();
        int mainInterface = dev.getInterface();
        int maxPacketSize = dev.getMaxPacketSize();

        System.out.println("Main Interface: " + mainInterface + "\nAlternate   Interface: " + altInterface + " \nMax Packet Size: " + maxPacketSize);

          dev.controlMsg(USB.REQ_TYPE_RECIP_DEVICE,USB.REQ_GET_STATUS,0,0,data,0,2000,false);

        //dev.writeBulk(0x81, data,  data.length, 2000, false);

        dev.readBulk(0x81, readData, readData.length, 2000, false);

        logData(readData);

        dev.close();

Here are the details on the device.

Usb_Bus bus-0
Usb_Device \\.\libusb0-0001--0x0bda-0x2838
    Usb_Device_Descriptor idVendor: 0xbda, idProduct: 0x2838
    Usb_Config_Descriptor bNumInterfaces: 0x1
        Usb_Interface num_altsetting: 0x1
            Usb_Interface_Descriptor bNumEndpoints: 0x1
                Usb_Endpoint_Descriptor bEndpointAddress: 0x81

Any help is much appreciated.

[uniederer]

What happens if you send this control message? Error messages? Exceptions?

[Wnt2bsleepin]

Yes, it throws an exception.

ch.ntb.usb.USBException: LibusbJava.controlMsg: libusb0-dll:err [control_msg] sending control message failed, win error: The parameter is incorrect.

The specific line is

dev.controlMsg(USB.REQ_TYPE_DIR_HOST_TO_DEVICE,USB.REQ_GET_STATUS,0,0,data,0,2000,false);

I also followed this guide to determine what to send for the Get-Status request.