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package com.orbekk.net;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class BroadcastListener {
private int port;
private Logger logger = LoggerFactory.getLogger(getClass());
DatagramSocket socket;
public BroadcastListener(int port) {
this.port = port;
}
public synchronized DatagramPacket listen() {
logger.debug("Waiting for broadcast on port " + port);
try {
if (socket == null) {
socket = new DatagramSocket(null);
socket.setReuseAddress(true);
socket.bind(new InetSocketAddress(port));
}
} catch (SocketException e) {
logger.warn("Failed to create socket.", e.fillInStackTrace());
return null;
}
try {
socket.setBroadcast(true);
} catch (SocketException e) {
logger.warn("Exception: {}", e);
}
byte[] buffer = new byte[2048];
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
try {
socket.receive(packet);
} catch (IOException e) {
logger.warn("Exception when listening for broadcast: {}", e);
return null;
}
String address = packet.getAddress().getHostAddress();
logger.debug("Received broadcast from " + address +
": " + new String(packet.getData(), 0, packet.getLength()));
return packet;
}
public void interrupt() {
socket.close();
}
public static void main(String[] args) {
int port = Integer.parseInt(args[0]);
BroadcastListener listener = new BroadcastListener(port);
System.out.println("Received broadcast: " + listener.listen());
}
}
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