Added basic auto discovery functionality

- Servers can advertise themselves
- Clients can detect servers on their local network

Tags: #story[1247]

src/main/java/seng302/visualiser/ServerListener.java

@@ -0,0 +1,56 @@
+package seng302.visualiser;
+
+import seng302.gameServer.ServerAdvertiser;
+
+import javax.jmdns.JmDNS;
+import javax.jmdns.ServiceEvent;
+import javax.jmdns.ServiceListener;
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+
+public class ServerListener{
+    private static ServerListener instance;
+    private ServerListenerDelegate delegate;
+    private JmDNS jmdns = null;
+
+    private class GameServerListener implements ServiceListener {
+        GameServerListener(){
+            System.out.println("Created GSL instance");
+        }
+
+        @Override
+        public void serviceAdded(ServiceEvent event) {
+            delegate.serverDetected(event.getName(), "", 123, event.getInfo().getInet4Addresses().toString());
+        }
+
+        @Override
+        public void serviceRemoved(ServiceEvent event) {
+            delegate.serverRemoved(event.getName());
+        }
+
+        @Override
+        public void serviceResolved(ServiceEvent event) {
+            // Do nothing
+        }
+    }
+
+    private ServerListener() throws IOException {
+        jmdns = JmDNS.create(InetAddress.getLocalHost());
+        jmdns.addServiceListener(ServerAdvertiser.SERVICE_TYPE, new GameServerListener());
+    }
+
+    public static ServerListener getInstance() throws IOException {
+        if (instance == null){
+            instance = new ServerListener();
+        }
+
+        return instance;
+    }
+
+    public void setDelegate(ServerListenerDelegate delegate){
+        this.delegate = delegate;
+    }
+
+
+}

src/main/java/seng302/visualiser/ServerListenerDelegate.java

@@ -0,0 +1,6 @@
+package seng302.visualiser;
+
+public interface ServerListenerDelegate {
+    void serverDetected(String serverName, String mapName, Integer placesLeft, String serverAddress);
+    void serverRemoved(String serverName);
+}