Simple EJB session client - problems with the JNDI lookup

I trying to make a simple  EJB session client work (I'm running the client from within Oracle9i Jdeveloper) but I get the following error:

javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file:  java.naming.factory.initial
      at javax.naming.spi.NamingManager.getInitialContext(NamingManager.java:640)
      at javax.naming.InitialContext.getDefaultInitCtx(InitialContext.java:243)
      at javax.naming.InitialContext.getURLOrDefaultInitCtx(InitialContext.java:280)
      at javax.naming.InitialContext.lookup(InitialContext.java:347)
      at examples.HelloClient.main(HelloClient.java:36)

Please help

Here is the code:

package examples;

import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Properties;

/** This class is an example of client code which invokes
 * methods on a simple stateless session bean. */
public class HelloClient {

      public static void main(String[] args) throws Exception {
            /* Setup properties for JNDI initialization.
             * These properties will be read-in from
             * the command-line. */
            Properties props = System.getProperties();

            /* Obtain the JNDI initial context.
             * The initial context is a starting point for
             * connecting to a JNDI tree. We choose our JNDI
             * driver, the network location of the server, etc
             * by passing in the environment properties. */
            Context ctx = new InitialContext(props);

            /* Get a reference to the home object - the
             * factory for Hello EJB Objects */
            Object obj = ctx.lookup("HelloHome");


            /* Home objects are RMI-IIOP objects, and so
             * they must be cast into RMI-IIOP objects
             * using a special RMI-IIOP cast. */
            HelloHome home = (HelloHome)
                  javax.rmi.PortableRemoteObject.narrow(
                        obj, HelloHome.class);

            /* Use the factory to create the Hello EJB Object */
            Hello hello = home.create();

            /* Call the hello() method on the EJB object.  The
             * EJB object will delegate the call to the bean,
             * receive the result, and return it to us.
             *
             * Print the result to the screen. */
            System.out.println(hello.hello());

            /* Done with EJB Object, so remove it.
             * The container will destroy the EJB object. */
            hello.remove();
      }
}

package examples;

import javax.ejb.SessionContext;

/**
 * Stateless session bean */
public class HelloBean implements javax.ejb.SessionBean
{
    // EJB-required methods
    public void ejbCreate()
    {
        System.out.println("ejbCreate()");
    }

    public void ejbRemove()
    {
        System.out.println("ejbRemove()");
    }

    public void ejbActivate()
    {
        System.out.println("ejbActivate()");
    }

    public void ejbPassivate()
    {
        System.out.println("ejbPassivate()");
    }

    public void setSessionContext(SessionContext ctx)
    {
        System.out.println("setSessionContext()");
    }

    // Business methods
    public String hello()
    {
        System.out.println("hello()");
        return "Hello, World!";
    }
}

package examples;
/** This is the HelloBean remote interface. */
public interface Hello extends javax.ejb.EJBObject
{
  /* The one method - hello - returns a greeting to the client. */
  public String hello() throws java.rmi.RemoteException;
}

package examples;
/**This is the home interface for HelloBean.*/
public interface HelloHome extends javax.ejb.EJBHome
{
    /** This method creates the EJB Object.
     * @return The newly created EJB Object. */
    Hello create() throws java.rmi.RemoteException,
        javax.ejb.CreateException;
}

package examples;
/**This is the HelloBean local interface.*/
public interface HelloLocal extends javax.ejb.EJBLocalObject
{
  /** The one method - hello - returns a greeting to the client. */
  public String hello();
}

package examples;
public interface HelloLocalHome extends javax.ejb.EJBLocalHome
{
    /**This method creates the EJB Object.
     * @return The newly created EJB Object. */
    HelloLocal create() throws javax.ejb.CreateException;
}

I also need somone to make a simple example of how to invoke a EJB entity object from with the session bean