OpenEnergyMonitorUDPConnector.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.openenergymonitor.protocol;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;
import java.nio.ByteBuffer;
import java.util.Arrays;

import org.openhab.binding.openenergymonitor.internal.OpenEnergyMonitorException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Connector for UDP communication.
 *
 * @author Pauli Anttila
 * @since 1.4.0
 */
public class OpenEnergyMonitorUDPConnector extends OpenEnergyMonitorConnector {

    private static final Logger logger = LoggerFactory.getLogger(OpenEnergyMonitorUDPConnector.class);

    static final int MAX_PACKET_SIZE = 255;

    int port = 9997;
    DatagramSocket socket = null;

    public OpenEnergyMonitorUDPConnector(int port) {

        if (port > 0) {
            this.port = port;
        }
    }

    @Override
    public void connect() throws OpenEnergyMonitorException {

        if (socket == null) {
            try {
                socket = new DatagramSocket(port);
                logger.debug("Open Energy Monitor UDP message listener started");

            } catch (SocketException e) {
                throw new OpenEnergyMonitorException(e);
            }
        }
    }

    @Override
    public void disconnect() throws OpenEnergyMonitorException {

        if (socket != null) {
            socket.close();
            socket = null;
        }
    }

    @Override
    public byte[] receiveDatagram() throws OpenEnergyMonitorException {

        try {

            if (socket == null) {
                socket = new DatagramSocket(port);
            }

            // Create a packet
            DatagramPacket packet = new DatagramPacket(new byte[MAX_PACKET_SIZE], MAX_PACKET_SIZE);

            // Receive a packet (blocking)
            socket.receive(packet);

            String[] bytes = new String(Arrays.copyOfRange(packet.getData(), 0, packet.getLength() - 1)).split(" ");

            ByteBuffer bytebuf = ByteBuffer.allocate(bytes.length);

            for (int i = 0; i < bytes.length; i++) {
                if (bytes[i].isEmpty() == false) {
                    byte b = (byte) Integer.parseInt(bytes[i]);
                    bytebuf.put(b);
                }
            }

            return bytebuf.array();

        } catch (SocketException e) {

            throw new OpenEnergyMonitorException(e);

        } catch (IOException e) {

            throw new OpenEnergyMonitorException(e);

        } catch (NumberFormatException e) {

            throw new OpenEnergyMonitorException(e);
        }

    }
}