diff --git a/ws2012/P2P/uebungen/4/src/peer/Node.java b/ws2012/P2P/uebungen/4/src/peer/Node.java
index aa19464f..12378a3d 100644
--- a/ws2012/P2P/uebungen/4/src/peer/Node.java
+++ b/ws2012/P2P/uebungen/4/src/peer/Node.java
@@ -30,6 +30,7 @@ public class Node {
 	private UDPListen udpListen;
 
 	public Node() {
+		//System.setProperty("java.net.preferIPv4Stack" , "true"); // optional IPv4 (mac, windows)
 		try {
 			channel = DatagramChannel.open();
 			channel.socket().bind(null);