1 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed OmniORB II Michael E. Kounavis Dept. of Electrical Engineering Columbia University Tutorial 3 12 November, 1998 Implementing a Session Controller

2 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed The Problem Consider three Internet hosts H1, H2 and H3. H1 transmits video packets to H3 via H2 and the session is controlled by a CORBA-based distributed system. This system comprises a ReceiverServer object running on H3, a NodeServer object running on H2 and a SessionController object running at a location different from H1, H2 or H3. A CORBA client runs on H1. The ReceiverServer object interface supports the opening of a UDP socket and the allocation of a free port for receiving packets. The NodeServer object interface supports the opening of a UDP socket, the allocation of a free port, and the forwarding of packets from the allocated port to a specified IP address and destination port. The creation of a datapath link between H1, H2 and H3 is hidden from H1 which interacts only with the SessionController object to establish the datapath.

3 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed NodeServer ReceiverServer SessionController CORBA client createSession(H3) returns H2, port2 receiverSetup() returns port flowSetup(H3, port) returns port H1 H2 H3 The Solution I

4 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed The Solution II interface NodeServer { void flowSetup( in string destHost, in short destPort, out short allocPort); } interface ReceiverServer { void receiverSetup ( out short allocPort); } interface SessionController { void createSession ( in string destHost, out string nextHop, out short nextPort ); }

5 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed The assignment –Assume that the NodeServer and ReceiverServer objects are implemented and running - Build the Session Controller - Build the CORBA client - Setup a datapath link using the services of the ReceiverServer and NodeServer objects and - Transmit your address so that it successfully received by the ReceiverServer object.

6 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Then... The ReceiverServer sends you an notifying of you of the successful reception of your message

7 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Hints I SessionController is both a client and a server It is a client to the NodeServer and ReceiverServer objects It is a server to your CORBA client Naming Service common to all students: Register your servers under your own path with your own context and object name NodeServer is bound to the path “midterm/NodeServer” with kind attributes set to “midterm_context” and “Object” respectively

8 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Hints II ReceiverServer is bound to the path “midterm/ReceiverServer” with kind attributes set to “midterm_context” and “Object” respectively Look at the solution to assignment II for the details of writing a server Your sender uses a UDP socket to transmit data to the receiver. You don’t need to use connect() this time. Destination IP address and port are returned by the createSession() method;

9 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Hints III You asume that the SessionController knows a-priori the location of H2, H3 NodeServer and ReceiverServer run on the hosts: harpsichord.comet.columbia.edu (MNL lab) wormwhole.ee.columbia.edu (Intel Lab)

10 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Writing a server (revision) First get a reference to ORB and BOA CORBA::ORB_ptr orb = CORBA::ORB_init(argc, argv, “omniORB2”); CORBA::ORB_ptr boa = orb->BOA_init(argc, argv, “omniORB2_BOA”); Instantiate the implementation object Echo_i *my_obj = new Echo_i(); myobj->_obj_is_ready(boa); Get an object reference (in order to bind to a name) Echo_var myobjRef = my_obj->_this(); Call impl_is_ready() boa->impl_is_ready();

11 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Using the naming service The first time you register your server you invoke bind_new_context(CosNaming::Name contextName) and bind(CosNaming::Name objectName) methods If the server has allready been registered invoke resolve (CosNaming::Name contextName) and rebind(CosNaming::Name objectName) methods

12 Distributed Telecommunications Systems Columbia University comet.columbia.edu/distributed Implementing the client-server Invoke methods supported by the NodeServer and ReceiverServer objects at the body of the creareSession() method of the SessionController_i class Use the orb and boa variables to get object references to these servers It is preferable to declare orb and boa as external variables GOOD LUCK!