[Home]	[About]
[Screenshots]	[Download]
[News]	[Community]
[Documentation]	[Manual]
[Bugs & Requests]	[Wiki]

/home/tetron/hack/vos/apps/tutorials/vostut3client.cc

Go to the documentation of this file.

/* Third VOS tutorial.  Local and Remote Vobjects and Messages.

   This tutorial file covers:
   - The difference between local and remote Vobjects
   - Accessing a remote Vobject
   - Creating a message and filling its fields
   - Sending a message to another Vobject

   This file (vostut3client.cc) is released into the public domain.  No
   restrictions are placed on its use, distribution or inclusion into
   other works. */

#include <vos/vos/vos.hh>

#ifdef WIN32
#define sleep(x) _sleep(x)
#endif

using namespace VUtil;
using namespace VOS;

// You must run this program after running vostut3server.

int main(int argc, char** argv)
{
    std::cout << "VOS Tutorial 3 Client\n\n";

    Site localsite;
    localsite.addSiteExtension(new LocalVipSiteExtension());

    // If the server process reports that it is using a different port
    // that 4231 then you will need to supply it on the command line.

    std::string siteurl;
    if(argc > 1) siteurl = argv[1];
    else siteurl = "vip://localhost:4231";

    try {
        /* The primary purpose of VOS is to allow transparent access to
           Vobjects, whether they are local or remote.  A "local" Vobject
           resides in the same process and address space as this application.
           It does not involve any sort of network activity (even a
           loopback socket) to manipulate a local Vobject.  A "remote"
           Vobject is anything which requires some sort of network
           activity to access.

           Vobjects are located using URLs.  The URL expresses the
           hostname and port of the site the Vobject resides upon,
           and the name of the object we want to access.  The static
           method findObjectFromRoot() takes care of connecting to the
           remote site, getting information about the Vobject and
           creating an instance of RemoteVobject which will represent
           the Vobject in our application.  */

        vRef<Vobject> primus = Vobject::findObjectFromRoot(siteurl + "/primus");


        // All the methods we demonstrated in the previous tutorial
        // are available.  Compare the following output to the same
        // code in the server:
        vRef<Site> site = primus->getSite();

        std::cout << "vostut3client: Vobject site name is: " << primus->getSiteName() << "\n";
        std::cout << "vostut3client: Vobject URL is: " << primus->getURLstr() << "\n";
        std::cout << "vostut3client: Vobject site is: " << site->getURLstr() << "\n";
        std::cout << "vostut3client: Our local site is: " << localsite.getURLstr() << "\n";

        std::cout << "vostut3client: Primus is local? " << (primus->isLocal() ? "yes" : "no") << "\n";
        std::cout << "vostut3client: Primus is remote? " << (primus->isRemote() ? "yes" : "no") << "\n";


        /* Vobjects can exchange messages with one another.  One way
           to think about a Vobject is as a mailbox: an address which
           can send and receive messages intended for a certain part
           of your application.  Let's say hello to the "primus"
           object.
        */

        /* Messages are reference counted and should always be
           assigned to a vRef<>.  When assigning a bare pointer to a
           smart pointer, you must tell it whether to increment the
           reference count or not.  A true value for the second
           parameter means increment, a false value means do not
           increment.  Normally you supply "true", but when an object
           is newly created, its reference count is already set to 1.
           Since we want the smart pointer to delete the object when
           we are done with it, we must tell vRef<> not to increment
           the pointer, so that when it is done it will decrement it
           to 0 and actually delete the object.
        */
        vRef<Message> m(new Message(), false);

        /* It seem odd that we need to say that the message type of a
           message is "message" but in fact there are a few different
           types of messages with different semantics.  A simple
           "message" is sent directly from one Vobject to another.
           Other messages types are covered in a later tutorial.
        */
        m->setType("message");

        // The message is directed to the primus Vobject.  You should
        // always use the full URL of the Vobject you are sending to.
        m->setTo(primus->getURLstr());

        // The message comes from our local site.
        m->setFrom(localsite.getURLstr());

        // The method.  This is the action expressed by this message.
        m->setMethod("tutorial:hello");

        /* Now we add some fields.  Fields of a VOS message are
           ordered and consist of a key and a value.  The first
           parameter is the key, and the second parameter is the value
           associated with that key.  Fields are ordered and
           distinguished by position, so keys may appear more than
           once. */

        m->appendField("unus", "one");
        m->appendField("word", "Caesar");
        m->appendField("unus", "ichi");
        m->appendField("duo", "two");

        /* Send the messages to the "primus" Vobject.  That's it!
           Simple!
        */
        std::cout << "vostut3client: sending message...\n";
        primus->sendMessage(m);

        std::cout << "vostut3client: waiting 1 second\n";
        sleep(1);

        /* The following exceptions may be emitted by
           Vobject::findObjectFromRoot():
        */
    } catch(NoSuchSiteError e) {
        // The site we wanted to access doesn't exist (we couldn't connect to it)
        std::cout << "Error!  " << e.what() << "\n";

    } catch(NoSuchObjectError e) {
        // The site exists, but there is no object by that name
        std::cout << "Error!  " << e.what() << "\n";

    } catch(AccessControlError e) {
        // We are not permitted to access this Vobject
        std::cout << "Error!  " << e.what() << "\n";

    } catch(RemoteError e) {
        // Something else bad happened, perhaps a remote site took too
        // long to reply and we timed out and gave up.
        std::cout << "Error!  " << e.what() << "\n";

    } catch(BadURLError e) {
        // We couldn't parse the URL!
        std::cout << "Error!  " << e.what() << "\n";
    }
    std::cout << "vostut3client: done\n";
    // We've either sent off our message or handled an exception, so
    // let the program run to completion...
}