--- jsmpp-2.1.0/src/java/main/org/jsmpp/session/AbstractSessionContext.java	2009-07-22 09:40:48.000000000 +0100
+++ jsmpp-2.1.0-m/src/java/main/org/jsmpp/session/AbstractSessionContext.java	2014-04-03 11:30:30.000000000 +0100
@@ -14,7 +14,7 @@
  */
 package org.jsmpp.session;
 
-import java.util.ArrayList;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.List;
 
 import org.jsmpp.bean.BindType;
@@ -29,7 +29,7 @@
 public abstract class AbstractSessionContext implements SessionContext {
     private static final Logger logger = LoggerFactory.getLogger(AbstractSessionContext.class);
     private long lastActivityTimestamp;
-    private List<SessionStateListener> sessionStateListeners = new ArrayList<SessionStateListener>();
+    private List<SessionStateListener> sessionStateListeners = new CopyOnWriteArrayList<SessionStateListener>();
     
     public AbstractSessionContext() {
     }
@@ -64,17 +64,23 @@
     
     public void addSessionStateListener(
             SessionStateListener l) {
-        sessionStateListeners.add(l);
+        synchronized (sessionStateListeners) {
+            sessionStateListeners.add(l);
+        }
     }
     
     public void removeSessionStateListener(SessionStateListener l) {
-        sessionStateListeners.remove(l);
+        synchronized (sessionStateListeners) {
+            sessionStateListeners.remove(l);
+        }
     }
     
     protected void fireStateChanged(SessionState newState,
             SessionState oldState, Object source) {
-        for (SessionStateListener l : sessionStateListeners) {
-            l.onStateChange(newState, oldState, source);
+        synchronized (sessionStateListeners) {
+            for (SessionStateListener l : sessionStateListeners) {
+                l.onStateChange(newState, oldState, source);
+            }
         }
     }