Read file by modbus RTU using J2MOD

Question

I have a device connected via a serial port using the Modbus protocol. I learned how to read input registers, write holding registers, but I can't read files. To do this, the command 0x14 must be used, this is provided by the method ReadFileRecordRequest.

Below is my code but after executing I get an error com.ghgande.j2mod.modbus.ModbusException: Assertion failed, transaction not executable Where I made mistake?

import com.ghgande.j2mod.modbus.ModbusException;
import com.ghgande.j2mod.modbus.io.ModbusSerialTransaction;
import com.ghgande.j2mod.modbus.msg.*;
import net.wimpi.modbus.net.SerialConnection;
import net.wimpi.modbus.util.SerialParameters;


public class j2mod {

    public static void main(String[] args) {

        ModbusSerialTransaction trans = null;
        ReadFileRecordRequest req = null;
        ReadFileRecordResponse res = null;

        SerialConnection con = null;

        int unitid = 1; // the unit identifier we will be talking to
        int repeat = 1; // a loop for repeating the transaction

        // Set port settings
        SerialParameters params = new SerialParameters();

        params.setPortName("COM482");
        params.setBaudRate("9600");
        params.setDatabits("8");
        params.setParity("NONE");
        params.setStopbits("1");
        params.setEncoding("rtu");
        params.setEcho(false);

        // Open connection
        con = new SerialConnection(params); // set connection with parameters
        try {
            con.open(); // open
        } catch (Exception e) {
            e.printStackTrace();
        }

        // 4. Open the connection
        try {

            // 5. Prepare a request
            req = new ReadFileRecordRequest();
            req.setUnitID(unitid);
            req.setHeadless();

            // 6. Prepare a transaction
            trans = new ModbusSerialTransaction();
            trans.setRequest(req);

            int k = 0;
            do {
                trans.setTransDelayMS(50);
                trans.execute();
                res = (ReadFileRecordResponse) trans.getResponse();
                for (int n = 0; n < res.getByteCount(); n++) {
                    System.out.println("Word " + n + "=" + res.getRecordCount());
                }
                k++;
            } while (k < repeat);
            con.close();
            // 8. Close the connection
        } catch (ModbusException ex) {
            System.out.print(ex);
        }
    }
}

Please help me find the error

I'm trying to output the reading result to the console