WolNode.java

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package org.rosbuilding.wol;

import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

import org.ros.message.MessageListener;
import org.ros.namespace.GraphName;
import org.ros.node.AbstractNodeMain;
import org.ros.node.ConnectedNode;
import org.ros.node.topic.Subscriber;

public class WolNode extends AbstractNodeMain
                                                implements MessageListener<std_msgs.String> {

        private static final String SUB_CMD = "wol";
        private static final int PORT = 9;

        private transient Subscriber<std_msgs.String> subscriberWol;

        private transient String prefix;
        private transient ConnectedNode connectedNode;
        private transient String network;

        @Override
        public GraphName getDefaultNodeName() {
                return GraphName.of("/system_wol");
        }

        @Override
        public void onStart(ConnectedNode connectedNode) {
                super.onStart(connectedNode);
                this.connectedNode = connectedNode;

                this.loadParameters();

                this.subscriberWol = this.connectedNode.newSubscriber(
                                                SUB_CMD,
                                                std_msgs.String._TYPE);
                this.subscriberWol.addMessageListener(this);
        }

        @Override
        public void onNewMessage(std_msgs.String msg) {
                try {
                        byte[] macBytes = getMacBytes(msg.getData());
                        byte[] bytes = new byte[6 + 16 * macBytes.length];
                        for (int i = 0; i < 6; i++) {
                                bytes[i] = (byte) 0xff;
                        }
                        for (int i = 6; i < bytes.length; i += macBytes.length) {
                                System.arraycopy(macBytes, 0, bytes, i, macBytes.length);
                        }

                        InetAddress address = InetAddress.getByName(this.network);
                        DatagramPacket packet = new DatagramPacket(
                                        bytes,
                                        bytes.length,
                                        address,
                                        PORT);
                        DatagramSocket socket = new DatagramSocket();
                        socket.send(packet);
                        socket.close();

                        this.connectedNode.getLog().info("Wake-on-LAN packet sent. For : " + msg.getData());
                } catch (Exception e) {
                        this.connectedNode.getLog().error("Failed to send Wake-on-LAN packet: " + e.getMessage() );
                }
        }

        private void loadParameters() {
                this.prefix = this.connectedNode.getParameterTree()
                                .getString("~tf_prefix", "");

                if (!this.prefix.equals("")) {
                    this.prefix = String.format("/%s/", this.prefix);
                }

                this.network = this.connectedNode.getParameterTree()
                                .getString("~network", "255.255.255.255");
        }

        private static byte[] getMacBytes(String macStr) throws IllegalArgumentException {
                byte[] bytes = new byte[6];
                String[] hex = macStr.split("(\\:|\\-)");
                if (hex.length != 6) {
                        throw new IllegalArgumentException("Invalid MAC address.");
                }
                try {
                        for (int i = 0; i < 6; i++) {
                                bytes[i] = (byte) Integer.parseInt(hex[i], 16);
                        }
                } catch (NumberFormatException e) {
                        throw new IllegalArgumentException(
                                        "Invalid hex digit in MAC address.");
                }
                return bytes;
        }

}