modbusudptransaction.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
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 ***/
package net.wimpi.modbus.io;

import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusException;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.ModbusSlaveException;
import net.wimpi.modbus.msg.ExceptionResponse;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.net.UDPMasterConnection;
import net.wimpi.modbus.net.UDPTerminal;

/**
 * Class implementing the <tt>ModbusTransaction</tt>
 * interface for the UDP transport mechanism.
 *
 * @author Dieter Wimberger
 * @version 1.2rc1 (09/11/2004)
 */
public class ModbusUDPTransaction
    implements ModbusTransaction {

  //class attributes
  private static int c_TransactionID =
      Modbus.DEFAULT_TRANSACTION_ID;

  //instance attributes and associations
  private UDPTerminal m_Terminal;
  private ModbusTransport m_IO;
  private ModbusRequest m_Request;
  private ModbusResponse m_Response;
  private boolean m_ValidityCheck =
      Modbus.DEFAULT_VALIDITYCHECK;
  private int m_Retries = Modbus.DEFAULT_RETRIES;
  private int m_RetryCounter = 0;

  /**
   * Constructs a new <tt>ModbusUDPTransaction</tt>
   * instance.
   */
  public ModbusUDPTransaction() {
  }//constructor

  /**
   * Constructs a new <tt>ModbusUDPTransaction</tt>
   * instance with a given <tt>ModbusRequest</tt> to
   * be send when the transaction is executed.
   * <p>
   * @param request a <tt>ModbusRequest</tt> instance.
   */
  public ModbusUDPTransaction(ModbusRequest request) {
    setRequest(request);
  }//constructor

  /**
   * Constructs a new <tt>ModbusUDPTransaction</tt>
   * instance with a given <tt>UDPTerminal</tt> to
   * be used for transactions.
   * <p>
   * @param terminal a <tt>UDPTerminal</tt> instance.
   */
  public ModbusUDPTransaction(UDPTerminal terminal) {
    setTerminal(terminal);
  }//constructor

  /**
   * Constructs a new <tt>ModbusUDPTransaction</tt>
   * instance with a given <tt>ModbusUDPConnection</tt>
   * to be used for transactions.
   * <p>
   * @param con a <tt>ModbusUDPConnection</tt> instance.
   */
  public ModbusUDPTransaction(UDPMasterConnection con) {
    setTerminal(con.getTerminal());
  }//constructor

  /**
   * Sets the terminal on which this <tt>ModbusTransaction</tt>
   * should be executed.<p>
   *
   * @param terminal a <tt>UDPSlaveTerminal</tt>.
   */
  public void setTerminal(UDPTerminal terminal) {
    m_Terminal = terminal;
    if (terminal.isActive()) {
      m_IO = terminal.getModbusTransport();
    }
  }//setConnection

  public void setRequest(ModbusRequest req) {
    m_Request = req;
    //m_Response = req.getResponse();
  }//setRequest

  public ModbusRequest getRequest() {
    return m_Request;
  }//getRequest

  public ModbusResponse getResponse() {
    return m_Response;
  }//getResponse

  public int getTransactionID() {
    return c_TransactionID;
  }//getTransactionID

  public void setCheckingValidity(boolean b) {
    m_ValidityCheck = b;
  }//setCheckingValidity

  public boolean isCheckingValidity() {
    return m_ValidityCheck;
  }//isCheckingValidity


  public int getRetries() {
    return m_Retries;
  }//getRetries

  public void setRetries(int num) {
    m_Retries = num;
  }//setRetries

  public void execute() throws ModbusIOException,
      ModbusSlaveException,
      ModbusException {

    //1. assert executeability
    assertExecutable();
    //2. open the connection if not connected
    if (!m_Terminal.isActive()) {
      try {
        m_Terminal.activate();
        m_IO = m_Terminal.getModbusTransport();
      } catch (Exception ex) {
        throw new ModbusIOException("Activation failed.");

      }
    }

    //3. Retry transaction m_Retries times, in case of
    //I/O Exception problems.
    m_RetryCounter = 0;
    while (m_RetryCounter <= m_Retries) {
      try {
        //3. write request, and read response,
        //   while holding the lock on the IO object
        synchronized (m_IO) {
          //write request message
          m_IO.writeMessage(m_Request);
          //read response message
          m_Response = m_IO.readResponse();
          break;
        }
      } catch (ModbusIOException ex) {
        m_RetryCounter++;
        continue;
      }
    }

    //4. deal with "application level" exceptions
    if (m_Response instanceof ExceptionResponse) {
      throw new ModbusSlaveException(
          ((ExceptionResponse) m_Response).getExceptionCode()
      );
    }

    if (isCheckingValidity()) {
      checkValidity();
    }

    //toggle the id
    toggleTransactionID();
  }//execute

  /**
   * Asserts if this <tt>ModbusTCPTransaction</tt> is
   * executable.
   *
   * @throws ModbusException if this transaction cannot be
   * asserted as executable.
   */
  private void assertExecutable()
      throws ModbusException {
    if (m_Request == null ||
        m_Terminal == null) {
      throw new ModbusException(
          "Assertion failed, transaction not executable"
      );
    }
  }//assertExecuteable

  /**
   * Checks the validity of the transaction, by
   * checking if the values of the response correspond
   * to the values of the request.
   *
   * @throws ModbusException if this transaction has not been valid.
   */
  private void checkValidity() throws ModbusException {
    //1.check transaction number
    //if(m_Request.getTransactionID()!=m_Response.getTransactionID()) {

    //}

  }//checkValidity

  /**
   * Toggles the transaction identifier, to ensure
   * that each transaction has a distinctive
   * identifier.<br>
   * When the maximum value of 65535 has been reached,
   * the identifiers will start from zero again.
   */
  private void toggleTransactionID() {
    if (isCheckingValidity()) {
      if (c_TransactionID == Modbus.MAX_TRANSACTION_ID) {
        c_TransactionID = 0;
      } else {
        c_TransactionID++;
      }
    }
    m_Request.setTransactionID(getTransactionID());
  }//toggleTransactionID

}//class ModbusUDPTransaction