CS603 Communication Mechanisms: DCE RPC (cont.)

1. CS603Communication Mechanisms:DCE 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_reply[REPLY_SIZE] ); }

3. Using defined interface:Client /* greet_client.c - Client of "greet" interface. usage: greet_client <CDS pathname>*/ #include <stdio.h> #include <dce/rpc.h> #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 reply[REPLY_SIZE]; /* Start importing servers using the name specified on the command line. */ rpc_ns_binding_import_begin(rpc_c_ns_syntax_default, (unsigned_char_p_t) argv[1], 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 interface:Server /* greet_manager.c - Implementation of "greet" interface. */ #include <stdio.h> #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 interface:Setting up listener /* greet_server.c - usage: greet_server <CDS pathname> */ #include <stdio.h> #include <dce/dce_error.h> #include <dce/rpc.h> #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 interface:Server /* 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) argv[1], 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_default, &status); ERROR_CHECK(status, "Can't start listening for calls"); }

7. CS603Communication Mechanisms:Java 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/HelloServer"); message = obj.sayHello(); System.out.println(message); } catch (Exception e) { System.out.println("HelloClient exception: " + e.getMessage()); e.printStackTrace(); } } }

17. Java RMI:Example 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 Example:Compile and Run • javac Hello.java HelloServer.java HelloClient.java • rmic –d `pwd` HelloServer • rmiregistry & # not in same directory • java -Djava.rmi.server.codebase=file:///`pwd`/-Djava.security.policy=opensocket HelloServer • opensocket: grant { permission java.net.SocketPermission "*", "connect"; }; • Java HelloClient