I think I have found the problem. In ClassLoadingAwareObjectInputStream.java the load() method makes a call to Class.forName().
For the primitive types (int, boolean, etc.) this would result in a call similar to: Class.forName("int", false, loader); //Where loader is the Applet2ClassLoader Since Applet2ClassLoader is a URLClassLoader and "int.class" is not in the jar cache it pulled down from the server at the start of application, it is going to try and go to the server to resolve this class. In the event of a network failure, this will result in the ClassLoader having to wait for the socket timeout. (see stacktrace in previous post) Once this socket timeout occurs, the load() method then attempts to lookup the class in the primitive HashMap that is statically initialized. This returns the class for the int and the deserialization continues on. At first it seemed like the messages were failing to be received but it turned out they were just taking a very long time to be deserialized. This problem can be avoided by changing the order in which ClassLoadingAwareObjectInputStream tries to resolve the class. Here is the change I made to the load() method: Please let me know how I can o about getting this incorporated into the ActiveMQ trunk. Thanks. private Class<?> load(String className, ClassLoader... cl) throws ClassNotFoundException { //Check to see if this is a primitive first final Class<?> clazz = (Class<?>) primClasses.get(className); if (clazz != null) { return clazz; //return the primitive class found in the map } else { for (ClassLoader loader : cl) { try { return Class.forName(className, false, loader); //for applets this may be a URLClassLoader } catch (Exception ex) { // ignore } } //if we still haven't found the class, use the fallback return Class.forName(className, false, FALLBACK_CLASS_LOADER); } } -- View this message in context: http://activemq.2283324.n4.nabble.com/Applet-Class-Loader-Problems-tp4671835p4671856.html Sent from the ActiveMQ - User mailing list archive at Nabble.com.