RMI - Remote Method Invocation

[Ray Dawson]

I know this will be really silly question to ask but I have to

I have trying to get this RMI thing to work but I have found that RMI have been changed significantly after Java 5, i.e we don't need to use rmic

Honestly, I have no clue what RMI is all about
So could you someone give me some good tutorials on RMI perhaps very basic ones!

I found a tutorial.

RemoteInterface.java

import java.rmi.*;

public interface RemoteInterface extends Remote
{
  public int add(int x,int y)throws Exception;
}

ServerImplements.java

import java.rmi.*;
import java.rmi.server.*;
import java.lang.String;

interface RemoteInterface extends Remote
{
  public int add(int x,int y)throws Exception;
}

public class ServerImplements extends 
 UnicastRemoteObject implements RemoteInterface
  {
  public ServerImplements()throws Exception
  {
  super();
  }
  public int add(int x,int y)
  {
  return (x+y);
  }
}

Server.java

import java.rmi.*;
import java.net.*;

public class  Server
{
  public static void main(String args[])
  {
  try
  {
  ServerImplements s=new ServerImplements();
  Naming.rebind("SERVICE",s);
  System.out.println("Server Started ");
  }
  catch(Exception e)
  {
  System.out.println(e.getMessage());
  }
  }

}

Client.java

import java.rmi.*;
import java.io.*;


public class Client
{
public static void main(String args[])
  {
 try
  {
 String ip="rmi://192.168.1.97/RMIAPPLICATION";
 RemoteInterface s=
   (RemoteInterface)Naming.lookup(ip);
 System.out.println("sum: "+ s.add(1,3));
  }
 catch(Exception e)
  {
  System.out.println(e.getMessage());
  e.printStackTrace();
  }
  }
}

Steps for executions

javac RemoteInterface.java

javac ServerImplements.java

rmic ServerImplements

javac Server.java

javac Client.java

start rmiregistry

start java server

java Client

I found this & I implemented the code as one, like

Server

import java.rmi.*;
import java.net.*;
import java.rmi.server.*;
import java.lang.String;


interface RemoteInterface extends Remote
{
  public int add(int x,int y)throws Exception;
}

class ServerImplements extends UnicastRemoteObject implements RemoteInterface
  {
  public ServerImplements()throws Exception
  {
    super();
  }
  public int add(int x,int y)
  {
    return (x+y);
  }
}

public class  Server
{
  public static void main(String args[])
  {
    try
    {
        ServerImplements s=new ServerImplements();
        Naming.rebind("SERVICE",s);
        System.out.println("Server Started ");
    }
    catch(Exception e)
    {
        System.out.println(e.getMessage());
    }
  }

}

And Client as

import java.rmi.*;
import java.io.*;


public class ServiceClient
{
  public static void main(String args[])
  {
      try
      {
        String ip="rmi://localhost/RMIAPPLICATION";
        RemoteInterface s = (RemoteInterface)Naming.lookup(ip);
        System.out.println("sum: "+ s.add(1,3));
      }
      catch(Exception e)
      {
        System.out.println(e.getMessage());
        e.printStackTrace();
       }
  }
}

When I run this it gives me this error :

Connection refused to host: localhost; nested exception is: 
	java.net.ConnectException: Connection refused: connect

Why do I even need to create an extra class for ServerImplements.java.
I don't understand can't we just create our server & specify its location & client simply connects to it ??

And can't we simply run the server.java & then client.java instead of the long process ??

BTW, I'm running this on BlueJ


Sorry, I'm the biggest noob on this forum

[Javin Paul]

In real world you rarely coding RMI with hand there are much better alternatives like web services. even if you need than I would go and use spring framework which will enable RMI with just few configuration without all mess of Remote interface and registry etc.

[Ray Dawson]

I need help with RMI ASAP, I have to use RMI & I dont have any alternatives

[Javin Paul]

check this out if it helps http://download.oracle.com/javase/1.4.2/docs/guide/rmi/getstart.doc.html

[John Jai]

Ray Dawson wrote:I need help with RMI ASAP, I have to use RMI & I dont have any alternatives

Please Ease Up... Please quote the source where you took the programs.

[Ray Dawson]

John Jai wrote:

Ray Dawson wrote:I need help with RMI ASAP, I have to use RMI & I dont have any alternatives

Please Ease Up... Please quote the source where you took the programs.

http://www.roseindia.net/tutorials/rmi/RMI-Example-1.shtml

[John Jai]

The service name in the Client.java is different than hosted in the Server.java. It should be

String ip="rmi://localhost/SERVICE";

[Campbell Ritchie]

As with your other thread, I am moving it.