SqueezeboxServerDiscoverer.java

package fr.phelep.java.squeezebox;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.util.ArrayList;

public class SqueezeboxServerDiscoverer {

    private static final int        DISCOVERY_PORT = 3483;
    private static final int        TIMEOUT_MS = 2500;
    private static final String     DISCOVERY_PACKET = "eIPAD\0NAME\0JSON\0VERS\0";

    private int             ipAddress;
    private int             netmask;
    private DatagramSocket          socket;
    private ArrayList<SqueezeboxServer> servers = new ArrayList<SqueezeboxServer>();


    public SqueezeboxServerDiscoverer( int ipAddress, int netmask ) throws IOException {
        this.ipAddress = ipAddress;
        this.netmask = netmask;

            this.socket = new DatagramSocket(DISCOVERY_PORT);
        this.socket.setBroadcast(true);
        this.socket.setSoTimeout(TIMEOUT_MS);

        this.sendDiscoveryRequest();
        this.listenForResponses();
        this.socket.close();
    }

    private void sendDiscoveryRequest() throws IOException {
        DatagramPacket packet = new DatagramPacket(DISCOVERY_PACKET.getBytes(),
                DISCOVERY_PACKET.length(), getBroadcastAddress(), DISCOVERY_PORT);
        this.socket.send(packet);
    }

    private InetAddress getBroadcastAddress() throws IOException {
        int broadcast = (this.ipAddress & this.netmask) | ~this.netmask;
        byte[] quads = new byte[4];
        for (int k = 0; k < 4; k++)
            quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);

        return InetAddress.getByAddress(quads);
    }

    private void listenForResponses() throws IOException {
        byte[] buf = new byte[256];
        try {
            while (true) {
                DatagramPacket packet = new DatagramPacket(buf, buf.length);
                this.socket.receive(packet);
                buf = packet.getData();
                int i = 1;
                int l;
                String t;
                String v;

                if( (char)buf[0] == 'E' ) {
                    String  ipAddress   = packet.getAddress().getHostAddress();
                    String  version     = null;
                    String  name        = null;
                    int port        = -1;

                    while( i< packet.getLength() ) {
                        t = new String(buf,i,4);
                        l = (int) buf[i+4];
                        v = new String(buf,i+5,l);
                        i = i + 5 + l;
                        if( t.equals("JSON") ) {
                            port = Integer.parseInt(v);
                        } else if( t.equals("NAME" ) ) {
                            name = v;
                        } else if( t.equals("VERS") ) {
                            version = v;
                        }
                    }

                    if( port > 0 ) {
                        this.servers.add(new SqueezeboxServer(ipAddress, port, name, version));
                    }
                }
            }
        } catch (SocketTimeoutException e) {
            // Should handle this sometime
        }
    }

    public int serversCount() {
        return this.servers.size();
    }

    public SqueezeboxServer getServer(int index) {
        return this.servers.get(index);
    }

}