diff --git a/src/main/java/com/jenkov/nioserver/ISocketIdListener.java b/src/main/java/com/jenkov/nioserver/ISocketIdListener.java
new file mode 100644
index 0000000..6368e57
--- /dev/null
+++ b/src/main/java/com/jenkov/nioserver/ISocketIdListener.java
@@ -0,0 +1,25 @@
+package com.jenkov.nioserver;
+
+/**
+ * Project: <strong>java-nio-server</strong><br>
+ * File: <strong>ISocketIdListener.java</strong><br>
+ * Created: <strong>03.01.2020</strong><br>
+ * 
+ * @author Kai S. K. Engelbart
+ */
+public interface ISocketIdListener {
+
+	/**
+	 * Is invoked when a new {@link Socket} is registered by the server
+	 * 
+	 * @param socketId the ID of the newly registered socket
+	 */
+	void socketRegistered(long socketId);
+
+	/**
+	 * Is invoked when a {@link Socket} is cancelled by the server
+	 * 
+	 * @param socketId the ID of the cancelled socket
+	 */
+	void socketCancelled(long socketId);
+}
diff --git a/src/main/java/com/jenkov/nioserver/Socket.java b/src/main/java/com/jenkov/nioserver/Socket.java
index 9cad6ea..9361986 100644
--- a/src/main/java/com/jenkov/nioserver/Socket.java
+++ b/src/main/java/com/jenkov/nioserver/Socket.java
@@ -47,5 +47,4 @@ public class Socket {
 
 		return totalBytesWritten;
 	}
-
 }
diff --git a/src/main/java/com/jenkov/nioserver/SocketProcessor.java b/src/main/java/com/jenkov/nioserver/SocketProcessor.java
index f05e76b..27575f2 100644
--- a/src/main/java/com/jenkov/nioserver/SocketProcessor.java
+++ b/src/main/java/com/jenkov/nioserver/SocketProcessor.java
@@ -51,6 +51,8 @@ public class SocketProcessor implements Runnable {
 	private Set<Socket>	emptyToNonEmptySockets	= new HashSet<>();
 	private Set<Socket>	nonEmptyToEmptySockets	= new HashSet<>();
 
+	private Set<ISocketIdListener> socketIdListeners = new HashSet<>();
+
 	public SocketProcessor(Queue<Socket> inboundSocketQueue, MessageBuffer readMessageBuffer, MessageBuffer writeMessageBuffer,
 			IMessageReaderFactory messageReaderFactory, IMessageProcessor messageProcessor) throws IOException {
 		this.inboundSocketQueue = inboundSocketQueue;
@@ -97,6 +99,7 @@ public class SocketProcessor implements Runnable {
 			newSocket.messageWriter = new MessageWriter();
 
 			socketMap.put(newSocket.socketId, newSocket);
+			socketIdListeners.forEach(l -> l.socketRegistered(nextSocketId - 1));
 
 			SelectionKey key = newSocket.socketChannel.register(readSelector, SelectionKey.OP_READ);
 			key.attach(newSocket);
@@ -121,6 +124,10 @@ public class SocketProcessor implements Runnable {
 		}
 	}
 
+	public void registerSocketIdListener(ISocketIdListener listener) {
+		socketIdListeners.add(listener);
+	}
+
 	private void readFromSocket(SelectionKey key) throws IOException {
 		Socket socket = (Socket) key.attachment();
 		socket.messageReader.read(socket, this.readByteBuffer);
@@ -138,6 +145,7 @@ public class SocketProcessor implements Runnable {
 		if (socket.endOfStreamReached) {
 			System.out.println("Socket closed: " + socket.socketId);
 			socketMap.remove(socket.socketId);
+			socketIdListeners.forEach(l -> l.socketCancelled(socket.socketId));
 			key.attach(null);
 			key.cancel();
 			key.channel().close();