Hi everybody!! I'm new using Tomcat, instead I'm new developing web applications, so I need help and patient... I'm trying to make a applet-servlet communication thru Apache-Tomcat cooperation. Before I tried it with a Blazix web server, but it was just for tests, because the web server was installed locally in a PC.. and it works perfect and I got the Applet-Servlet communication. Now, I'm trying to do the same with Apache-Tomcat installed in a Solaris Server, and I had been trying that communication for days and I can't yet. I'm trying to make an application that can solve a educational situation, like registration of subjects in my database (Oracle). In this case the Applet only is used like an interface for the user. The user can register a new subject thru the Applet, then the Applet send an object to the Servlet thru a serializable class (Ubc.class) [all this using ObjectInputStream and ObjectOutputStream classes]. The Servlet recieve the Ubc object and interpret it from register all data like a field in a table of the database. Anyway, if the user only want to see all the list of subjects, the Applet sends the url of the Servlet next to a parameter (UserOption = "Display") and the servlet recieve the parameter and make a vector with Ubc objects filling them with the database information and finally the Servlet sends the vector with a writeObject method to the Applet, whose displays the information in the screen. And that's all!!. So, in Tomcat I create the next stucture: tomcat-directory/webapps/proyectoprueba2/WEB-INF/classes/ ---in classes directory store the servlet classes and the ubc.class in Apache I did this: apache-directory/htdocs/proyectoprueba2/ ---in proyectoprueba2 directory store the html file that invokes the applet class, of course, I store the applet class, and the ubc.class. Now I invoke the html file and it works very well, but when I tried to register a subject invoking the servlet thru the applet, I only got an error: Error: 500 Location: /proyectoprueba2/servlet/Servlet3 Internal Servlet Error: java.lang.NullPointerException at java.lang.ClassLoader.resolveClass0(Native Method) at java.lang.ClassLoader.resolveClass0(Compiled Code) at java.lang.ClassLoader.resolveClass(Compiled Code) at org.apache.tomcat.loader.AdaptiveClassLoader.loadClass(Compiled Code) at org.apache.tomcat.loader.AdaptiveServletLoader.loadClass(AdaptiveServletLoader.java:174) at org.apache.tomcat.core.ServletWrapper.loadServlet(Compiled Code) at org.apache.tomcat.core.ServletWrapper.init(Compiled Code) at org.apache.tomcat.core.Handler.service(Handler.java:254) at org.apache.tomcat.core.ServletWrapper.service(ServletWrapper.java:372) at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:797) at org.apache.tomcat.core.ContextManager.service(ContextManager.java:743) at org.apache.tomcat.service.http.HttpConnectionHandler.processConnection(HttpConnectionHandler.java:213) at org.apache.tomcat.service.TcpWorkerThread.runIt(Compiled Code) at org.apache.tomcat.util.ThreadPool$ControlRunnable.run(Compiled Code) at java.lang.Thread.run(Compiled Code) All the classes I did are part of a proyectoprueba2 package, so I had to create the directory... Where do I have put the Ubc class in Tomcat?? I'm working with Tomcat in a stand alone mode. Do I need to connect it with Apache?? HOW??? I had been testing other servlets that are like "HelloWorld"... they only print a text.. and they works perfect with Tomcat... Can you help me??? I'll be waiting for your help.... Thank you advanced.. Nancy.