java.lang.UnsatisfiedLinkError: No implementation found for java .io.FileDescriptor android_serialport_api.SerialPort.open(string ,int ,int)

Question

while I am working on integrating Java CCNET SDK to my Android application ,I can not run ccnet commands from my app to the cashcode .

programe to execute command

        IConnection comPort = new sPort();
        comPort.setPath(_serialPort.path);//"/dev/ttyS2"
        comPort.setBaudRate(_serialPort.baudRate);//9600
        comPort.setDelay(_serialPort.delay);//1000;
        _ccnet = new CCNET(_device, comPort);//_device=DEVICE.Bill_Validator;
try{
       Answer answer = _ccnet.RunCommand(command);
}catch{Exception e}{
Log.i(e);
}

the above code generates the following Error

java.lang.UnsatisfiedLinkError: No implementation found for java .io.FileDescriptor android_serialport_api.SerialPort.open(string ,int ,int) (tried Java_android_1serialport_1api_SerialPort_open and Java_android_1serialport_1api_SerialPort_open_Ljava_lang_String_2ll)

**My folder structure **