private String tostr(byte[] buffer) {
    try {
        int length = 0;
        for (int i = 0; i < buffer.length; ++i) {
            if (buffer[i] == 0) {
                length = i;
                break;
            }
        }
        return new String(buffer, 0, length, "UTF-8");
    } catch (Exception e) {

        return "";
    }
}