Remote Method Invocation (RMI)

1. Remote Method Invocation (RMI) • RMI is a mechanism for communicating (only) between two machines running Java Virtual Machines

3. The stub object (on machine A) has to • build an information block thats consists of • an identifier of the remote object to be used, • an operation number describing the method to be called and • the marshalled parameters (method parameters have to be encoded into a format suitable for transporting them across the net) • send this information to the server

4. The tasks of the skeleton object (on machine B) are • to unmarshal the parameters, • to call the desired method on the real object lying on the server, • to capture the return value or exception of the call on the server, • to marshal this value, • to send a package consisting of the value in the marshalled form back to the stub on the client, machine A.

5. ArithmeticInterface.java

6. import java.rmi.*; public interface ArithmeticInterface extends Remote { int add(inta,int b)throws RemoteException; }

7. ArithmeticImplement.java

8. import java.rmi.*; import java.rmi.server.*; public class ArithmeticImplement extends UnicastRemoteObject implements ArithmeticInterface { intx,y; public ArithmeticImplement()throws RemoteException { super(); }

9. public int add(inta,int b)throws RemoteException { return a+b; } public static void main(String[] args)throws Exception { ArithmeticImplementaImp=new ArithmeticImplement(); Naming.rebind("rmi://localhost:1099/ArithmeticInterface",aImp); } }

10. ArithmeticClient.java

11. import java.rmi.*; import java.io.*; public class ArithmeticClient { public ArithmeticClient() { String rmObj="rmi://localhost:1099/ArithmeticInterface"; try{ ArithmeticInterfaceaInterf= ArithmeticInterface)Naming.lookup(rmObj); intx,y;

12. InputStreamReader ir=new InputStreamReader(System.in); BufferedReaderkbdInput=new BufferedReader(ir); System.out.println("Enter nos:"); x=Integer.parseInt(kbdInput.readLine()); y=Integer.parseInt(kbdInput.readLine()); System.out.println("Result is "+aInterf.add(x,y)); } catch (Exception e) {} }

13. public static void main(String[] args)throws Exception { ArithmeticClient client=new ArithmeticClient(); } }

14. Executing RMI

15. Compile all Java files - javac *.java Create Stub & Skelton - rmicArithmeticImplement Start RMI registry - First Command Prompt rmiregistry 1099 Start Server - Second Command Prompt java ArithmeticImplement Start Client - Third Command Prompt java ArithmeticClient