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I'm developing a ModbusRTU Master Over TCP/IP Interface to read a ModbusRTU electricity meters data. the meters are working over RS485 network, and I implemented a RS485/RS232 and RS232/Ethernet(TCP/IP) Adapter via a java application. The application implement a ModbusRTU Master (client) over the TCP/IP protocol via TCP/Socket.

The application pretends to be a jmodbus library extension.

But when the application send a modbus request to the electricity meter, don't receive a response.

the meter is a Contrel EMD-D3B-485 (technical info here-> http://www.contrel.it/data/products/tech/1325595876_EMC-D3bIM450-Ev2.1 .pdf)

the RS232 / Ethernet(tcp/ip) converter is a Wiznete WIZ110SR (link here-> http://www.olimex.cl/product_info.php?cPath=76_83&products_id=455& amp;product__name=Conversor_Serial_RS232_a_Ethernet_WIZ110SR)

the source code is the following (only to debug and test):

package testModelo;
import Utils.CCITTcrc;
import java.io.*;
import java.net.InetAddress;
import java.net.Socket;
import jmodbus.ByteUtils;

/**
 *
 * @author Michael Venegas, DreamIT Software -> mvenegas(in)dreamit(dot)cl
 */
public class testSocket {

    public static void main(String args[]){
        
/*

	the Utils.CCITTcrc calculate a Modbus (hight and low CRC Modbus -> posted by nancy here: http://www.control.com/thread/1026215359)
	the jmodbus.ByteUtils convert the bytes to hex.

	The electricity Meter containt the following data points:
	ID meter -> 01
	Data Address -> 4096
	Data Length -> 16

*/        

	int idDevice = 1;
	int modbusFunction = 3;
	int dataAddress = 4096;
	int dataAddressLength = 16;

	//the byte traza is a new byte containt the modbusRTU message
        byte traza[] = new byte[6];
        traza[0] = (byte)(idDevice & 0xFF);
        traza[1] = (byte)(modbusFunction & 0xFF);
        traza[2] = (byte)((dataAddress >> 8) & 0xFF);
        traza[3] = (byte)((dataAddress >> 0) & 0xFF);
        traza[4] = (byte)((dataAddressLength >> 8) & 0xFF);
        traza[5] = (byte)((dataAddressLength >> 0) & 0xFF);

        //show the modbusRTU message
        for(int i=0; i<traza.length; i++){
            System.out.println(jmodbus.ByteUtils.toHex(traza[i]));
        }
        
	//calculate the CRC Modbus message
        CCITTcrc crc = new CCITTcrc();
        byte ceerreces[] = crc.calc(traza, traza.length);
        
        //show the CRC Modbus message
        System.out.println(jmodbus.ByteUtils.toHex(ceerreces[0]));
        System.out.println(jmodbus.ByteUtils.toHex(ceerreces[1]));
        
        //create the full packet and concatenate the modbus message and modbus crc
        byte[] Packet = {traza[0],traza[1],traza[2],traza[3],traza[4],traza[5],ceerreces[0],ce erreces[1]};
        
	//the IP address and port of the RS232/Ethernet TCP/IP converter
        String host="192.168.0.190";
        int port = 5000;
        
        //the java socket
        Socket cliente;
        
        try {
            
            //create the socket
            cliente = new Socket(host,port);
            
	    //instanciate the input and output stream to communicate with the converter
            DataOutputStream salida_ = new DataOutputStream(cliente.getOutputStream());
            BufferedReader receivedPacket= new BufferedReader(new InputStreamReader(cliente.getInputStream()));
            
	    //show the data packet
            System.out.println("enviando packete..");
            System.out.println("Lo que se envia: "+ByteUtils.toHex(Packet, Packet.length));
            
            //sending the data packet
            salida_.flush();
            salida_.write(Packet);
            salida_.flush();
            
            System.out.println("Esperando recibir algo..");
            //waiting receive some data
            byte elem;
            byte[] bytes = new byte[1];
            for(int i=0; i< 1; i++){
                elem = (byte) receivedPacket.read();
                bytes[i] = elem;
                System.out.println(ByteUtils.toHex(elem));
            }
            
            
        } catch (IOException ex) {
            ex.printStackTrace();
        }
        
        
    }

}

thanks for any help.
I apologize from my English, but i'm a Chilean guy and i do not speak so well.

Best regards

Hello,

Try connect to modbus slave simulator (like Modsim), to see what your application is sending.

Regards,
Andrzej
www.modbus.pl

To expand on what Andrzej says, you have a complex chain of possible failures facing you, so start working your way down the chain.

1) confirm with wireshark that you send a single TCP packet and the Modbus/RTU is valid.

2) I personally would try using any Modbus master to poll the same request and confirm it looks 100% the same (aka: CRC byte order matches, no unexpected NULLs embedded, etc).

3) the wireshark will also confirm your TCP/serial box saw the request & sent the TCP ack.

4) if the TCP/serial box has stats, confirm it sent 8 bytes (or whatever size it should be).

5) then you get into the whole "Is my cable correct" between the TCP/serial box and meter. You need some somehow confirm this is correct - ideally with a volt meter - or if you are lucky, the Wiznete box's RS-232 port is 100% PC-like, then you can test the same cable directly.

- Lynn

The ip address of the converter is 192.168.0.190.

If i test from the modbus poll (trial) over a virtual "com" (the software and driver of the ethernet-rs232 converter, only for windows OS), the meter send a response, but when I send a request, no.

I'm reviewing the packets using wireshark but the packets are practically identical =S..

the packet screenshot of the software over a virtual "com" viewed from wireshark:
http://i.imgur.com/vDN3R.png

the packet screenshot of my application:
http://i.imgur.com/uuze5.png

any suggestion?

now i'll test my app using a virtual modbusRTU slave

maybe my app is not allowed for receive a response or those code block contain a programation error.

thanks
best regards

> the packet screenshot of the software over a virtual "com" viewed from wireshark:
> http://i.imgur.com/vDN3R.png

> the packet screenshot of my application:
> http://i.imgur.com/uuze5.png

Note that the 'virtual comm' Data Len is 17 bytes, while your own is 273 bytes?

Should not your own packet be exactly 4 bytes if you are sending a Report Slave ID request as RTU in a raw binary TCP socket?

- Lynn

You can try xMasterSlave for Modbus protocol at www.tgscada.com. It is a completely freeware.