add socket removal listeners

src/gov/nist/javax/sip/stack/NioTcpMessageChannel.java

@@ -243,6 +243,8 @@ protected void close(boolean removeSocket, boolean stopKeepAliveTask) {
 			if(stopKeepAliveTask) {
 				cancelPingKeepAliveTimeoutTaskIfStarted();
 			}
+
+			SocketRemovalListeners.send(this.getKey());
 		} catch (IOException e) {
 			logger.logError("Problem occured while closing", e);
 		}

src/gov/nist/javax/sip/stack/SocketRemovalListeners.java

@@ -0,0 +1,32 @@
+package gov.nist.javax.sip.stack;
+
+import java.util.Collection;
+import java.util.LinkedList;
+
+public class SocketRemovalListeners {
+
+    private static final Collection<Listener> listeners = new LinkedList();
+
+    public static interface Listener {
+        void socketRemoved(String channel);
+    }
+
+    public static void addListener(Listener listener) {
+        listeners.add(listener);
+    }
+
+    public static void clear() {
+        listeners.clear();
+    }
+
+    public static void send(String channel) {
+        for (Listener listener: listeners) {
+            try {
+                listener.socketRemoved(channel);
+            } catch (Exception e) {
+                System.err.println("Exception caught with message: " + e.getMessage());
+                e.printStackTrace();
+            }
+        }
+    }
+}