private String sendCheckCommand(IEZioLibrary eZioLib) {
        byte[] ret = new byte[100];
        int msgSize;
        eZioLib.sendcommand("~S,CHECK");

        for (int i = 0; i < 10; i++) {
            msgSize = eZioLib.RcvBuf(ret, ret.length);
            if (msgSize > 0) {
                break;
            }
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        String returnedString = new String(ret);

        if (returnedString.length() >= 2) {
            returnedString = returnedString.substring(returnedString.length() - 2, returnedString.length());
        }

        return returnedString;
    }