Summer Ahmad

Hello,

I'm new to RMI. I've been tying to run the well-known calculator example for 3 days now, but to no avail. I'm starting to give up learning RMI. Please help me discover why the remote method doesn't get invoked !!

On computer number 1 (which has the name "Server0" on the network), and specifically in a folder named "CALC" I have the following files :

Calculator.class (This is the interface)
----------------------------------------

public interface Calculator extends java.rmi.Remote { public int sub(int a, int b) throws java.rmi.RemoteException; }

CalculatorImpl.class (Implementation of the interface)
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import java.rmi.Naming; import java.rmi.*; public class CalculatorImpl extends java.rmi.server.UnicastRemoteObject implements Calculator { public CalculatorImpl() throws java.rmi.RemoteException { super(); } public int sub(int a, int b) throws java.rmi.RemoteException { return a-b; } public static void main(String[] args) { if (System.getSecurityManager() == null) System.setSecurityManager(new RMISecurityManager()); try { Calculator c = new CalculatorImpl(); Naming.rebind("rmi://Server0/CalculatorService", c); } catch (Exception e) {System.out.println ("Error binding");} } }

CalculatorImpl_Stub.class (stub generated using rmic)
-----------------------------------------------------
Automatically generated ...

java.policy
-----------
grant { permission java.net.SocketPermission "*:1024-65535", "connect,accept"; permission java.net.SocketPermission "*:80", "connect"; };


On this machine (Server0), I launched MS. DOS, unset the classpath, and ran rmiregistry :
C:\CALC>set classpath=
C:\CALC>rmiregistry

I then opened another instance of MS. DOS to set the classpath, set the security policty and run the server:
C:\CALC>set classpath=c:\calc
C:\CALC>java -Djava.security.policy=java.policy CalculatorImpl

So far, so good, No errors !

On the other machine, that is on the same network, I have the following files in a folder named "CALC" :

Calculator.class (This is the interface)
----------------------------------------
See code above.

CalculatorClient.java (This is the client)
------------------------------------------
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.net.MalformedURLException;
import java.rmi.NotBoundException;

public class CalculatorClient {

public static void main(String[] args) {
try {
Calculator c = (Calculator) Naming.lookup("rmi://Server0/CalculatorService");
System.out.println( c.sub(4, 3) );
}
catch (Exception e) {System.out.println("Error returning stub and invoking remote method on stub");}

}
}

java.policy
-----------
see code above


Similarly, I launched an instance of MS DOS and typed:
C:\CALC>set classpath=
C:\CALC>rmiregistry

Launched another instance and typed:
C:\CALC>set classpath=c:\calc
C:\CALC>java -Djava.security.policy=java.policy -Djava.rmi.server.codebase=http://Server0/CalculatorService/ CalculatorClient

An Exception was caught, and the msg "Error returning stub and invoking remote method on stub" was printed.

Any help will be greatly appreciated !