Serial connection - I/O Exception failed to read

[Julien Jakob]

Hello !
There is the following exception I can't resolve :

com.ghgande.j2mod.modbus.ModbusIOException: I/O exception - failed to read
        at com.ghgande.j2mod.modbus.io.ModbusASCIITransport.readResponseIn(Modbu
sASCIITransport.java:192)
        at com.ghgande.j2mod.modbus.io.ModbusSerialTransport.readResponse(Modbus
SerialTransport.java:124)
        at com.ghgande.j2mod.modbus.io.ModbusSerialTransaction.execute(ModbusSer
ialTransaction.java:147)
        at j2modTest.readOne(j2modTest.java:39)
        at j2modTest.main(j2modTest.java:59)

I really need help, can you figure out what's wrong with my code ? Here it is :

import java.net.*;
import java.io.*;
import com.ghgande.j2mod.modbus.*;
import com.ghgande.j2mod.modbus.facade.*;
import com.ghgande.j2mod.modbus.io.*;
import com.ghgande.j2mod.modbus.msg.*;
import com.ghgande.j2mod.modbus.net.*;
import com.ghgande.j2mod.modbus.util.*;

public class j2modTest {

    SerialConnection con;

    public j2modTest() {
        SerialParameters param = new SerialParameters();
        param.setPortName("COM4");
        this.con = new SerialConnection(param);
    }

    public void readOne(String jbus) {
        try {
            //Ouverture de la connexion
            this.con.open();

            //Preparation de la requete
            int ref = Integer.parseInt(jbus, 16);
            ReadMultipleRegistersRequest req = new ReadMultipleRegistersRequest(ref, 1);
            req.setUnitID(1);
            req.setHeadless(true);

            //Preparation de la transaction
            ModbusSerialTransaction trans = new ModbusSerialTransaction(this.con);
            trans.setRetries(5);
            trans.setRequest(req);

            //Execution de la transaction
            trans.execute();
            Thread.sleep(500);
            ReadMultipleRegistersResponse res = (ReadMultipleRegistersResponse) trans.getResponse();
            for (int j = 0; j < res.getWordCount(); j++) {
                System.out.println("Info " + j + " : " + res.getRegisterValue(j));
            }

            //Fermeture de la connexion
            this.con.close();
        }
        catch(Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public static void main(String[] args) {
        j2modTest t = new j2modTest();
        t.readOne("0130");
    }
}

The readOne() method is supposed to read one holding register.

I thank you in advance !

[Julien Jakob]

I have completely modified my code but I still get the exact same error.
(Most of it comes from the example in the cmd folder)
Here it is :

import java.io.IOException;
import java.util.Arrays;

import gnu.io.*;
import com.ghgande.j2mod.modbus.Modbus;
import com.ghgande.j2mod.modbus.ModbusException;
import com.ghgande.j2mod.modbus.io.*;
import com.ghgande.j2mod.modbus.msg.*;
import com.ghgande.j2mod.modbus.net.ModbusMasterFactory;
import com.ghgande.j2mod.modbus.procimg.Register;
import com.ghgande.j2mod.modbus.util.SerialParameters;

public class ReadHoldingRegistersTest {

    private static void printUsage() {
        System.out.println("java com.ghgande.j2mod.modbus.cmd.ReadHoldingRegistersTest"
                + " <address{:port{:unit}} [String]>"
                + " <base [int]> <count [int]> {<repeat [int]>}"
                + " Ici on ecrira par exemple : device:COM4:1 0130 1");
    }

    public static void main(String[] args) {
        ModbusRTUTransport transport = null;
        ModbusRequest req = null;
        ModbusTransaction trans = null;
        int ref = 0;
        int count = 0;
        int repeat = 1;
        int unit = 0;

        //Mise en place des parametres
        if (args.length < 3) {
            printUsage();
            System.exit(1);
        }

        try {
            try {
                //Ouverture de la connexion
                String parts[] = args[0].split(":");
                if (parts.length < 2)
                    throw new IllegalArgumentException("missing connection information");

                SerialParameters params = new SerialParameters();
                params.setPortName(parts[1]);

                try {
                    transport = new ModbusRTUTransport();
                    transport.setCommPort(new RXTXPort(params.getPortName()));
                    transport.setEcho(false);
                }
                catch (IOException e) {
                    transport = null;
                }

                if (transport == null) {
                    System.err.println("Cannot open " + args[0]);
                    System.exit(1);
                }

                ((ModbusSerialTransport) transport).setReceiveTimeout(500);
                if (System.getProperty("com.ghgande.j2mod.modbus.baud") != null)
                    ((ModbusSerialTransport) transport).setBaudRate(Integer.parseInt(System.getProperty("com.ghgande.j2mod.modbus.baud")));
                else
                    ((ModbusSerialTransport) transport).setBaudRate(9600);

                /*
                 * Certains appareils ne s'initialisent pas immediatement, 
                 * on leur laisse le temps
                 */
                Thread.sleep(2000);

                ref = Integer.parseInt(args[1], 16);
                count = Integer.parseInt(args[2]);

                if (args.length == 4)
                    repeat = Integer.parseInt(args[3]);

                if (parts.length >= 3)
                    unit = Integer.parseInt(parts[2]);

                String baud = System.getProperty("com.ghgande.j2mod.modbus.baud");
                if (baud != null)
                    ((ModbusRTUTransport) transport).setBaudRate(Integer.parseInt(baud));
            } 
            catch (Exception ex) {
                ex.printStackTrace();
                printUsage();
                System.exit(1);
            }

            //Creation de la requete
            req = new ReadMultipleRegistersRequest(ref, count);
            req.setUnitID(unit);

            //Preparation de la transaction
            trans = transport.createTransaction();
            trans.setRequest(req);
            req.setHeadless(true);

            if (Modbus.debug)
                System.out.println("Request: " + req.getHexMessage());

            //Execution de la transaction "repeat" fois

            for (int i = 0; i < repeat; i++) {
                try {
                    trans.execute();
                } 
                catch (ModbusException x) {
                    System.err.println(x.getMessage());
                    continue;
                }
                ModbusResponse res = trans.getResponse();

                if (Modbus.debug) {
                    if (res != null)
                        System.out.println("Response: " + res.getHexMessage());
                    else
                        System.err.println("No response to READ HOLDING request.");
                }

                if (res instanceof ExceptionResponse) {
                    ExceptionResponse exception = (ExceptionResponse) res;
                    System.out.println(exception);
                    continue;
                }

                if (! (res instanceof ReadMultipleRegistersResponse))
                    continue;

                ReadMultipleRegistersResponse data = (ReadMultipleRegistersResponse) res;
                Register values[] = data.getRegisters();

                System.out.println("Data: " + Arrays.toString(values));
            }
        } 
        catch (Exception ex) {
            ex.printStackTrace();
        }

        try {
            //Fermeture de la connexion
            if (transport != null)
                transport.close();
        } 
        catch (IOException e) {
            //Ne rien faire
        }
        System.exit(0);
    }
}