modbusseriallistener.java

jamod is an object oriented implementation of the Modbus protocol, realized 100 in Java. It allows

//License
/***
 * Java Modbus Library (jamod)
 * Copyright (c) 2002-2004, jamod development team
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 *
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 *
 * Neither the name of the author nor the names of its contributors
 * may be used to endorse or promote products derived from this software
 * without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS ``AS
 * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 ***/
package net.wimpi.modbus.net;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusCoupler;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.io.ModbusTransport;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.util.SerialParameters;

/**
 * Class that implements a ModbusTCPListener.<br>
 * If listening, it accepts incoming requests
 * passing them on to be handled.
 *
 * @author Dieter Wimberger
 * @version 1.2rc1 (09/11/2004)
 */
public class ModbusSerialListener {

  //Members
  private boolean m_Listening;               	//Flag for toggling listening/!listening
  private SerialConnection m_SerialCon;
  private static int c_RequestCounter = 0;          //counter for amount of requests

  /**
   * Constructs a new <tt>ModbusSerialListener</tt> instance.
   *
   * @param params a <tt>SerialParameters</tt> instance.
   */
  public ModbusSerialListener(SerialParameters params) {
    m_SerialCon = new SerialConnection(params);
    //System.out.println("Created connection.");
    listen();
  }//constructor

  /**
   * Listen to incoming messages.
   */
  private void listen() {
    try {
      m_Listening = true;
      m_SerialCon.open();
      //System.out.println("Opened Serial connection.");
      ModbusTransport transport = m_SerialCon.getModbusTransport();
      do {
        if (m_Listening) {
          try {
            //1. read the request
            ModbusRequest request = transport.readRequest();
            ModbusResponse response = null;

            //test if Process image exists
            if (ModbusCoupler.getReference().getProcessImage() == null) {
              response =
                  request.createExceptionResponse(Modbus.ILLEGAL_FUNCTION_EXCEPTION);
            } else {
              response = request.createResponse();
            }

            if (Modbus.debug)
              System.out.println("Request:" + request.getHexMessage());
            if (Modbus.debug)
              System.out.println("Response:" + response.getHexMessage());

            transport.writeMessage(response);

            count();
          } catch (ModbusIOException ex) {
            ex.printStackTrace();
            continue;
          }
        }
        //ensure nice multithreading behaviour on specific platforms

      } while (true);

    } catch (Exception e) {
      //FIXME: this is a major failure, how do we handle this
      e.printStackTrace();
    }
  }//listen

  /**
   * Sets the listening flag of this <tt>ModbusTCPListener</tt>.
   *
   * @param b true if listening (and accepting incoming connections),
   *        false otherwise.
   */
  public void setListening(boolean b) {
    m_Listening = b;
  }//setListening

  /**
   * Tests if this <tt>ModbusTCPListener</tt> is listening
   * and accepting incoming connections.
   *
   * @return true if listening (and accepting incoming connections),
   *          false otherwise.
   */
  public boolean isListening() {
    return m_Listening;
  }//isListening

  private void count() {
    c_RequestCounter++;
    if (c_RequestCounter == REQUESTS_TOGC) {
      System.gc();
      c_RequestCounter = 0;
    }
  }//count

  private static final int REQUESTS_TOGC = 15;

}//class ModbusTCPListener