New to Java RMI

Question

I am having problems with the following code that I am currently trying to understand RMI from Java head First, the following are meant to be part of an universal browser that the browser downloads and displays interactive Java GUIs. Can someone explain what I am doing wrong as I am still new to Java please?
import java.awt.*;
import javax.swing.*;
import java.rmi.*;
import java.awt.event.*;
public class ServiceBrowser {
   JPanel mainPanel;
   JComboBox serviceList;
   ServiceServer server;
   public void buildGUI() {
      JFrame frame = new JFrame("RMI Browser");
      mainPanel = new JPanel();
      frame.getContentPane().add(BorderLayout.CENTER, mainPanel);
      Object[] services = getServicesList();
      serviceList = new JComboBox(services);
      frame.getContentPane().add(BorderLayout.NORTH, serviceList);
      serviceList.addActionListener(new MyListListener());    
      frame.setSize(500,500);
      frame.setVisible(true);
   void loadService(Object serviceSelection) {
       try {
          Service svc = server.getService(serviceSelection);
          mainPanel.removeAll();
          mainPanel.add(svc.getGuiPanel());
          mainPanel.validate();
          mainPanel.repaint();
        } catch(Exception ex) {
           ex.printStackTrace();
   Object[] getServicesList() {
      Object obj = null;
      Object[] services = null;
      try {
          obj = Naming.lookup("rmi://127.0.0.1/ServiceServer");   
     catch(Exception ex) {
       ex.printStackTrace();
     server = (ServiceServer) obj;
      try {
        services = server.getServiceList();
      } catch(Exception ex) {
         ex.printStackTrace();
     return services;
   class MyListListener implements ActionListener {
      public void actionPerformed(ActionEvent ev) {
          // do things to get the selected service
          Object selection =  serviceList.getSelectedItem();
          loadService(selection);
  public static void main(String[] args) {
     new ServiceBrowser().buildGUI();
}I am able to compile the code but come up with the following error messages at runtime
java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is:
     java.net.ConnectException: Connection refused
     at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:601)
     at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:198)
     at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:184)
     at sun.rmi.server.UnicastRef.newCall(UnicastRef.java:322)
     at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
     at java.rmi.Naming.lookup(Naming.java:84)
     at ServiceBrowser.getServicesList(ServiceBrowser.java:53)
     at ServiceBrowser.buildGUI(ServiceBrowser.java:19)
     at ServiceBrowser.main(ServiceBrowser.java:82)
Caused by: java.net.ConnectException: Connection refused
     at java.net.PlainSocketImpl.socketConnect(Native Method)
     at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
     at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
     at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
     at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)
     at java.net.Socket.connect(Socket.java:529)
     at java.net.Socket.connect(Socket.java:478)
     at java.net.Socket.<init>(Socket.java:375)
     at java.net.Socket.<init>(Socket.java:189)
     at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
     at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
     at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:595)
     ... 8 more
java.lang.NullPointerException
     at ServiceBrowser.getServicesList(ServiceBrowser.java:64)
     at ServiceBrowser.buildGUI(ServiceBrowser.java:19)
     at ServiceBrowser.main(ServiceBrowser.java:82)
Exception in thread "main" java.lang.NullPointerException
     at javax.swing.DefaultComboBoxModel.<init>(DefaultComboBoxModel.java:53)
     at javax.swing.JComboBox.<init>(JComboBox.java:175)
     at ServiceBrowser.buildGUI(ServiceBrowser.java:21)
     at ServiceBrowser.main(ServiceBrowser.java:82)
The code for the remote implementation compile and runs, but the other code for services compiles but come back with the following error message at runtime:
Exception in thread "main" java.lang.NoSuchMethodError: main
I have included one of the services code below this happens with:
import javax.swing.*;
import java.awt.event.*;
import java.io.*;
public class DiceService implements Service {
    JLabel label;
    JComboBox numOfDice;
    public JPanel getGuiPanel() {
       JPanel panel = new JPanel();
       JButton button = new JButton("Roll 'em!");
       String[] choices = {"1", "2", "3", "4", "5"};
       numOfDice = new JComboBox(choices);
       label = new JLabel("dice values here");
       button.addActionListener(new RollEmListener());
       panel.add(numOfDice);
       panel.add(button);
       panel.add(label);
       return panel;
   public class RollEmListener implements ActionListener {
      public void actionPerformed(ActionEvent ev) {
         // roll the dice
         String diceOutput = "";
         String selection = (String)  numOfDice.getSelectedItem();
         int numOfDiceToRoll = Integer.parseInt(selection);
         for (int i = 0; i < numOfDiceToRoll; i++) {
            int r = (int) ((Math.random() * 6) + 1);
            diceOutput += (" " + r);
        label.setText(diceOutput);
}

Answer 1

how I do get suitable server running, can I not test the code on a local ip address first, i have included the remote implementation code below, can you advise how I can resolve this please or point me in the right direction?
import java.rmi.*;
import java.util.*;
import java.rmi.server.*;
public class ServiceServerImpl extends UnicastRemoteObject implements ServiceServer  {
    HashMap<String, Service> serviceList;
    public ServiceServerImpl() throws RemoteException {
       // start and set up services
       setUpServices();
   private void setUpServices() {
       serviceList = new HashMap<String, Service>();
       serviceList.put("Dice Rolling Service", new DiceService()); 
       serviceList.put("Day of the Week Service", new DayOfTheWeekService()); 
       serviceList.put("Visual Music Service", new MiniMusicService());  
    public Object[] getServiceList() {
       System.out.println("in remote");
       return serviceList.keySet().toArray();
    public Service getService(Object serviceKey) throws RemoteException {       
       Service theService = (Service) serviceList.get(serviceKey);      
       return theService;
    public static void main (String[] args) {
       try {
         Naming.rebind("ServiceServer", new ServiceServerImpl());
        } catch(Exception ex) { }
        System.out.println("Remote service is running");
}