CS603 Communication Mechanisms: DCE RPC (cont.)

1
CS603Communication MechanismsDCE RPC (cont.)

• 23 January 2002

2
Sample IDL formessage/reply RPC

• / greet.idl
• The "greet" interface. /
• uuid(3d6ead56-06e3-11ca-8dd1-826901beabcd),
  version(1.0)
• / import like_c_includes.idl /
• / type declarations (typedef) /
• interface greetif
• const long int REPLY_SIZE 100
• void greet(
• in handle_t h,
• in, string char client_greeting,
• out, string char server_replyREPLY_SI
  ZE
• )

3
Using defined interfaceClient

• / greet_client.c - Client of "greet" interface.
  usage greet_client ltCDS pathnamegt/
• include ltstdio.hgt include ltdce/rpc.hgt include
  "greet.h include "util.h"
• Int main(int argc, char argv)
• rpc_ns_handle_t import_context handle_t
  binding_h error_status_t status
• idl_char replyREPLY_SIZE
• / Start importing servers using the name
  specified on the command line. /
• rpc_ns_binding_import_begin(rpc_c_ns_syntax_de
  fault, (unsigned_char_p_t) argv1,
• greetif_v1_0_c_ifspec, NULL,
  import_context, status)
• ERROR_CHECK(status, "Can't begin import")
• / Import the first server (we could iterate
  here, but we'll just take the first one). /
• rpc_ns_binding_import_next(import_context,
  binding_h, status)
• ERROR_CHECK(status, "Can't import")
• / Make the remote call. /
• greet(binding_h, (idl_char ) "hello,
  server", reply)
• printf("The Greet Server said s\n", reply)

4
Using defined interfaceServer

• / greet_manager.c - Implementation of "greet"
  interface. /
• include ltstdio.hgt
• include "greet.h"
• void greet(
• handle_t h,
• idl_char client_greeting,
• idl_char server_reply
• )
• printf("The client says s\n",
  client_greeting)
• strcpy(server_reply, "Hi, client!")

5
Using defined interfaceSetting up listener

• / greet_server.c - usage greet_server ltCDS
  pathnamegt /
• include ltstdio.hgt
• include ltdce/dce_error.hgt
• include ltdce/rpc.hgt
• include "greet.h"
• include "util.h"
• Int main(int argc, char argv)
• unsigned32 status rpc_binding_vector_t
  binding_vector
• / Register interface with RPC runtime. /
• rpc_server_register_if(greetif_v1_0_s_ifspec,
  NULL, NULL, status)
• ERROR_CHECK(status, "Can't register
  interface")
• / Use all protocol sequences that are available.
  /
• rpc_server_use_all_protseqs(rpc_c_protseq_max_
  reqs_default, status)
• ERROR_CHECK(status, "Can't use protocol
  sequences")
• / Get the binding handles generated by the
  runtime. /
• rpc_server_inq_bindings(binding_vector,
  status)
• ERROR_CHECK(status, "Can't get bindings for
  server")

6
Using defined interfaceServer

• / Register assigned endpoints with endpoint
  mapper. /
• rpc_ep_register(greetif_v1_0_s_ifspec,
  binding_vector, NULL,
• (unsigned_char_p_t) "greet server version
  1.0", status)
• ERROR_CHECK(status, "Can't register with
  endpoint map")
• / Export ourselves into the CDS namespace. /
• rpc_ns_binding_export(
• rpc_c_ns_syntax_default,
  (unsigned_char_p_t) argv1,
• greetif_v1_0_s_ifspec, binding_vector,
  NULL, status)
• ERROR_CHECK(status, "Can't export into CDS
  namespace")
• / Start listening for calls. /
• printf("Listening...\n")
• rpc_server_listen(rpc_c_listen_max_calls_defau
  lt, status)
• ERROR_CHECK(status, "Can't start listening
  for calls")

7
CS603Communication MechanismsJava RMI

• 23 January 2002

8
Java RMI

• Overview
• Supports remote invocation of Java objects
• Key Java Object SerializationStream objects
  over the wire
• Language specific
• History
• Goal RPC for Java
• First release in JDK 1.0.2, used in Netscape 3.01
• Full support in JDK 1.1, intended for applets
• JDK 1.2 added persistent reference, custom
  protocols, more support for user control.

9
Java RMI

• Advantages
• True object-orientation Objects as arguments
  and values
• Mobile behavior Returned objects can execute on
  caller
• Integrated security
• Built-in concurrency (through Java threads)
• Disadvantages
• Java only
• Advertises support for non-Java
• But this is external to RMI requires Java on
  both sides

10
Java RMIComponents

• Base RMI classes
• Extend these to get RMI functionality
• Java compiler javac
• Recognizes RMI as integral part of language
• Interface compiler rmic
• Generates stubs from class files
• RMI Registry rmiregistry
• Directory service
• RMI Run-time activation system rmid
• Supports activatable objects that run only on
  demand

11
Java RMI classes

• Java.rmi.Remote
• Interface supporting remote objects
• java.rmi.server.UnicastRemoteObject
• Continuously running server
• java.rmi.activation.Activatable
• Server started by rmid daemon
• java.rmi.naming
• Lookup Returns stub given a name
• java.rmi.RMISecurityManager
• Validates rights to access downloaded object

12
Java RMIRegistry Operation
13
Java RMIObject Serialization

• Key difference from DCE Can send object to be
  invoked at remote site
• Allows objects as arguments/results
• Mechanism Object Serialization
• Object passed must inherit from serializable
• Provides methods to translate object to/from byte
  stream
• Security issues
• Ensure object not tampered with during
  transmission
• Solution Class-specific serializationThrow it
  on the programmer

14
Building a Java RMI Application

• Define remote interface
• Extend java.rmi.Remote
• Create server code
• Implements interface
• Creates security manager, registers with registry
• Create client code
• Define object as instance of interface
• Lookup object in registry
• Call object
• Compile and run
• Run rmic on compiled classes to create stubs
• Start registry
• Run server then client

15
Java RMISample interface

• import java.rmi.Remote
• import java.rmi.RemoteException
• public interface Hello extends Remote
• String sayHello() throws RemoteException

16
Java RMISample Client

• import java.rmi.Naming
• import java.rmi.RemoteException
• public class HelloClient
• public static void main(String args)
• String message "blank"
• Hello obj null
• try obj (Hello)Naming.lookup("//myhost/He
  lloServer")
• message obj.sayHello()
• System.out.println(message)
• catch (Exception e)
• System.out.println("HelloClient
  exception " e.getMessage())
• e.printStackTrace()

17
Java RMIExample Server

• import java.rmi.Naming
• import java.rmi.RemoteException
• import java.rmi.RMISecurityManager
• import java.rmi.server.UnicastRemoteObject
• public class HelloServer extends
  UnicastRemoteObject implements Hello
• public HelloServer() throws RemoteException
  super()
• public String sayHello() return "Hello
  World!"
• public static void main(String args)
• if (System.getSecurityManager() null)
• System.setSecurityManager(new
  RMISecurityManager())
• try HelloServer obj new HelloServer()
• Naming.rebind("//myhost/HelloServer",
  obj)
• System.out.println("HelloServer bound in
  registry")
• catch (Exception e)
• System.out.println("HelloServer err "
  e.getMessage())
• e.printStackTrace()

18
Java RMI ExampleCompile and Run

• javac Hello.java HelloServer.java
  HelloClient.java
• rmic d pwd HelloServer
• rmiregistry not in same directory
• java -Djava.rmi.server.codebasefile///pwd/-Dj
  ava.security.policyopensocket HelloServer
• opensocket grant permission java.net.SocketPerm
  ission "", "connect"
• Java HelloClient