diff --git a/ws2012/P2P/uebungen/4/src/node/Ack.java b/ws2012/P2P/uebungen/4/src/node/Ack.java
new file mode 100644
index 00000000..29bb167d
--- /dev/null
+++ b/ws2012/P2P/uebungen/4/src/node/Ack.java
@@ -0,0 +1,26 @@
+package node;
+
+import java.net.SocketAddress;
+import java.nio.ByteBuffer;
+
+public class Ack {
+
+	private SocketAddress address;
+	private ByteBuffer buf;
+
+	public Ack(SocketAddress address) {
+		this.address = address;
+	}
+
+	public boolean check(SocketAddress address) {
+		return this.address.toString().equals(address.toString());
+	}
+
+	public ByteBuffer getBuf() {
+		return buf;
+	}
+
+	public void setBuf(ByteBuffer buf) {
+		this.buf = buf;
+	}
+}
\ No newline at end of file
diff --git a/ws2012/P2P/uebungen/4/src/util/BufferUtil.java b/ws2012/P2P/uebungen/4/src/util/BufferUtil.java
new file mode 100644
index 00000000..8a866fe2
--- /dev/null
+++ b/ws2012/P2P/uebungen/4/src/util/BufferUtil.java
@@ -0,0 +1,18 @@
+package util;
+
+import java.nio.ByteBuffer;
+
+public class BufferUtil {
+
+	public static ByteBuffer clone(ByteBuffer original) {
+		ByteBuffer clone = ByteBuffer.allocate(original.capacity());
+
+		int oldPosition = original.position();
+		original.rewind();// copy from the beginning
+		clone.put(original);
+		// original.rewind();
+		original.position(oldPosition);
+		clone.flip();
+		return clone;
+	}
+}