/***
* Copyright 2002-2010 jamod development team
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
***/
package net.wimpi.modbus.io;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InterruptedIOException;
import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.ModbusIOException;
import net.wimpi.modbus.msg.ModbusMessage;
import net.wimpi.modbus.msg.ModbusRequest;
import net.wimpi.modbus.msg.ModbusResponse;
import net.wimpi.modbus.net.UDPTerminal;
/**
* Class that implements the Modbus UDP transport
* flavor.
*
* @author Dieter Wimberger
* @version 1.0 (29/04/2002)
*/
public class ModbusUDPTransport
implements ModbusTransport {
//instance attributes
private UDPTerminal m_Terminal;
private BytesOutputStream m_ByteOut;
private BytesInputStream m_ByteIn;
/**
* Constructs a new <tt>ModbusTransport</tt> instance,
* for a given <tt>UDPTerminal</tt>.
* <p>
* @param terminal the <tt>UDPTerminal</tt> used for message transport.
*/
public ModbusUDPTransport(UDPTerminal terminal) {
m_Terminal = terminal;
m_ByteOut = new BytesOutputStream(Modbus.MAX_MESSAGE_LENGTH);
m_ByteIn = new BytesInputStream(Modbus.MAX_MESSAGE_LENGTH);
}//constructor
public void close()
throws IOException {
//?
}//close
public void writeMessage(ModbusMessage msg)
throws ModbusIOException {
try {
synchronized (m_ByteOut) {
m_ByteOut.reset();
msg.writeTo((DataOutput) m_ByteOut);
m_Terminal.sendMessage(m_ByteOut.toByteArray());
}
} catch (Exception ex) {
throw new ModbusIOException("I/O exception - failed to write.");
}
}//write
public ModbusRequest readRequest()
throws ModbusIOException {
try {
ModbusRequest req = null;
synchronized (m_ByteIn) {
m_ByteIn.reset(m_Terminal.receiveMessage());
m_ByteIn.skip(7);
int functionCode = m_ByteIn.readUnsignedByte();
m_ByteIn.reset();
req = ModbusRequest.createModbusRequest(functionCode);
req.readFrom(m_ByteIn);
}
return req;
} catch (Exception ex) {
throw new ModbusIOException("I/O exception - failed to read.");
}
}//readRequest
public ModbusResponse readResponse()
throws ModbusIOException {
try {
ModbusResponse res = null;
synchronized (m_ByteIn) {
m_ByteIn.reset(m_Terminal.receiveMessage());
m_ByteIn.skip(7);
int functionCode = m_ByteIn.readUnsignedByte();
m_ByteIn.reset();
res = ModbusResponse.createModbusResponse(functionCode);
res.readFrom(m_ByteIn);
}
return res;
} catch (InterruptedIOException ioex) {
throw new ModbusIOException("Socket timed out.");
} catch (Exception ex) {
ex.printStackTrace();
throw new ModbusIOException("I/O exception - failed to read.");
}
}//readResponse
}//class ModbusUDPTransport