diff --git a/ws2012/P2P/uebungen/4/src/node/Ack.java b/ws2012/P2P/uebungen/4/src/node/Ack.java
index 9583db1e..9e90c87d 100644
--- a/ws2012/P2P/uebungen/4/src/node/Ack.java
+++ b/ws2012/P2P/uebungen/4/src/node/Ack.java
@@ -23,14 +23,10 @@ public class Ack {
     // The channel to re-send the message on
     private DatagramChannel channel;
 
-    OnAckReceive callback;
-
-    public Ack(int id, SocketAddress address, DatagramChannel channel,
-            OnAckReceive onReceive) {
+	public Ack(int id, SocketAddress address, DatagramChannel channel) {
         this.id = id;
         this.address = address;
         this.channel = channel;
-        this.callback = onReceive;
         startThread();
     }
 
@@ -58,10 +54,6 @@ public class Ack {
     }
 
     public void setReceived() {
-        if (callback != null) {
-            callback.onReceive();
-        }
-
         // Stop thread
         try {
             if (thread != null) {
diff --git a/ws2012/P2P/uebungen/4/src/node/Node.java b/ws2012/P2P/uebungen/4/src/node/Node.java
index 8947f246..4bb626da 100644
--- a/ws2012/P2P/uebungen/4/src/node/Node.java
+++ b/ws2012/P2P/uebungen/4/src/node/Node.java
@@ -40,8 +40,6 @@ public class Node {
 
 	private Random generator;
 
-    protected boolean receivedAckForLastInvite;
-
 	public Node() {
 		System.setProperty("java.net.preferIPv4Stack", "true");
 		generator = new Random(System.currentTimeMillis());
@@ -75,7 +73,6 @@ public class Node {
         LOGGER.log(Level.FINE, "Name: " + getName() + ", Spawning new node.");
 		Node newNode = new Node();
         addNeighbor(newNode.getAddress());
-        receivedAckForLastInvite = false;
 		sendInvite(newNode);
 
 		return newNode;
@@ -84,12 +81,7 @@ public class Node {
     private boolean sendInvite(final Node newNode) {
 		ByteBuffer buffer = ByteBuffer.allocate(BUF_SIZE);
 
-        Ack ack = generateAck(newNode.getAddress(), new OnAckReceive() {
-            @Override
-            public void onReceive() {
-                receivedAckForLastInvite = true;
-            }
-        });
+		Ack ack = generateAck(newNode.getAddress());
 
 		buffer.put(MessageType.INVITE);
 		buffer.putInt(ack.getId());
@@ -113,12 +105,12 @@ public class Node {
 	 *            the SocketAddress the ack should be received from
 	 * @return the identifier for this ack
 	 */
-    private Ack generateAck(final SocketAddress addr, OnAckReceive callback) {
+	private Ack generateAck(final SocketAddress addr) {
 		int ack_id = generator.nextInt();
         while (acks.containsKey(ack_id)) {
             ack_id = generator.nextInt();
         }
-        Ack newAck = new Ack(ack_id, addr, channel, callback);
+		Ack newAck = new Ack(ack_id, addr, channel);
 		
 		acks.put(ack_id, newAck);
 		return newAck;
@@ -223,6 +215,11 @@ public class Node {
     public void gatherInformationOfNetwork() {
 		network = new HashMap<String, List<String>>();
 
+		network.put(getName(), new ArrayList<String>());
+		for (SocketAddress n : neighbors) {
+			network.get(getName()).add(n.toString());
+		}
+
         try {
 			byte[] myAddr = BufferUtil.addrToBytes(((InetSocketAddress) channel
                     .getLocalAddress()));
@@ -268,7 +265,7 @@ public class Node {
         int idToRemove = getNeighborId(node);
         if (idToRemove != -1) {
             removed = neighbors.remove(idToRemove);
-            network.get(getName()).remove(node.toString());
+			network.get(getName()).remove(node.toString());
         }
 
         return removed != null;
@@ -279,7 +276,8 @@ public class Node {
 	 * from the network.
 	 */
 	public void leave() {
-        if (!receivedAckForLastInvite || neighbors.isEmpty()) {
+		// if (!receivedAckForLastInvite || neighbors.isEmpty()) {
+		if (!acks.isEmpty() || neighbors.isEmpty()) {
             // This means the bootstrapping has not been finished. Either I have
             // not been invited by a node, or the Node I invited didn't ack by
             // now
@@ -289,7 +287,7 @@ public class Node {
 
         for (int i = 0; i < neighbors.size(); i++) {
             ByteBuffer buffer = ByteBuffer.allocate(BUF_SIZE);
-            Ack ack = generateAck(neighbors.get(i), null);
+			Ack ack = generateAck(neighbors.get(i));
             buffer.put(MessageType.LEAVE);
             buffer.putInt(ack.getId());