I can not read the true values form Holding Register (DB10.DBW0) of  PLC. Need help.

I use PLC as Server and write the codes to hold values of   Holding Register (DB10.DBW0) like the Picture attach below.

And I use jamodModbus as client to write codes from PC to connect to PLC and read the values from of  Holding Register (DB10.DBW0).  

The result is: I can connect to PLC sucessfull, send the request to PLC but the vulues out put respond I get from Holding Register (DB10.DBW0) of  PLC alway zero (00). How can I fix this problem and please tell which code I use to get only values from Holding Register (DB10.DBW0) and change them to Decimal?

This is my codes from PC:

package testmodbus;

import java.lang.*;

import java.net.InetAddress;

import java.net.SocketTimeoutException;

import net.wimpi.modbus.Modbus;

import net.wimpi.modbus.ModbusSlaveException;

import net.wimpi.modbus.io.ModbusTCPTransaction;

import net.wimpi.modbus.msg.WriteCoilRequest;

import net.wimpi.modbus.msg.ReadInputRegistersRequest;

import net.wimpi.modbus.msg.ReadInputRegistersResponse;

import net.wimpi.modbus.net.TCPMasterConnection;

public class TestModbus {

    public static void main(String[] args) throws ModbusSlaveException, SocketTimeoutException{

        // TODO code application logic here

        try {

            /* The important instances of the class */

            TCPMasterConnection con = null; // the connection

            ModbusTCPTransaction trans = null; // the transaction

            ReadInputRegistersRequest rreq = null; // the read request

            ReadInputRegistersResponse rres = null; // the read response

            WriteCoilRequest req = null; // the write request

            int ref = 40000; //the reference; offset where to start reading from

            int count =0;

            int repeat = 2;

            /* Variables for storing the parameters */

            InetAddress addr = null; // the slave's address

            int port = Modbus.DEFAULT_PORT; // DEFAULT_PORT = 502.

            // 1. Setup ?":>the parameters

            addr = InetAddress.getByName("192.168.0.1"); // ** The address of PLC

            // 2. Open the connection

            con = new TCPMasterConnection(addr);

            con.setPort(port);

            con.connect();

            System.out.println("--- Message: Line:36 success --- ");

            System.out.println("Connect to PLC sucessfull!!");

            // ~~~~~~~~~~~~~~~~~~~~ The faulty Read Request ~~~~~~~~~~~~~~~~~~~~

//           // 3r. Prepare the READ request

rreq = new ReadInputRegistersRequest(ref, count);

            System.out.println("The reqquest values =" + rreq.getHexMessage());

           System.out.println("--- Message: Line:42 success --- ");

////            // 4r. Prepare the READ transaction

            trans = new ModbusTCPTransaction(con);

            trans.setRequest(rreq);

/            System.out.println("--- Message: Line:46 success --- ");

////            // 5r. Execute the READ transaction

            int k = 0;

            do {

            trans.execute();

            rres =  (ReadInputRegistersResponse) trans.getResponse();

            System.out.println("The reqquest values =" + rreq.getHexMessage());

            System.out.println("getHexMessage of resspond = "+ rres.getHexMessage());

             k++;

            }while (k<repeat);

            // 6. Close the connection

            con.close();

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}

And this is the out put I get from Console:

run:

--- Message: Line:36 success ---

Connect to PLC sucessfull!!

The reqquest values =00 00 00 00 00 06 00 04 9c 40 00 00

--- Message: Line:42 success ---

--- Message: Line:46 success ---

The reqquest values =00 01 00 00 00 06 00 04 9c 40 00 00

------------------------------------------------------------------------------------------
Split from S7-1200 Modbus TCP communication with Modbus Server.

Hello,

ok I try something to ask, how you know that you have success connection?

            // 2. Open the connection

            con = new TCPMasterConnection(addr);

            con.setPort(port);

            con.connect();

            System.out.println("--- Message: Line:36 success --- ");

            System.out.println("Connect to PLC sucessfull!!");

I mean that bold line command which make connection, because you don't have return value from it, so you don't know exactly if it success or not. You simply continue with console output that connection is succesfull, but I'm not sure about this. I recommend to you, if it's possible create return variables (you can check return value of success/not success) or debug with breakpoints to check if it is succesfull. I don't know from your post if PLC return some frame or this is only your received buffer filled with some 0-s or with something. Pls give info.

Hi!

Have you checked on the PLC side, what's in the ERROR and STATUS registers and if the DR becomes 1 when you read?

As a first step, you could also make sure that the PLC communicates with a client by using a modbus tester, e.g. this:

http://www.simplymodbus.ca/TCPclient.htm

If that works, then you can start with debugging your PC code.