apps/tutorials/vostut3client.cc

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/* 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/corelibs/vos/vos.hh>

// You must run this program after running vostut3server.

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

    LocalSocketSite localsite(&NoAccessControl::static_);

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

    string siteurl;
    if(argc > 1) siteurl = argv[1];
    else siteurl = "vop://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 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 accessed using URLs.  The URL expresses the
           hostname and port of the site this 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

        cout << "vostut3client: Vobject site name is: " << primus->getName() << "\n";
        cout << "vostut3client: Vobject URL is: " << primus->getURL().getString() << "\n";
        vRef<Site> site = primus->getSite();
        cout << "vostut3client: Vobject site is: " << site->getURL().getString() << "\n";
        cout << "vostut3client: Our local site is: " << localsite.getURL().getString() << "\n";

        cout << "vostut3client: Primus is local? " << primus->isLocal() << "\n";
        cout << "vostut3client: Primus is remote? " << primus->isRemote() << "\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<>.
        vRef<Message> m = new Message();

        /* This may seem a bit odd, but there are actually several
           different types of messages.  A "message" type is the
           simplest, being sent directly from one Vobject to another.
           Other messages types are processed differently (these are
           discussed 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->getURL().getString());

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

        // 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 of the insertField() messages is the position to
           insert the new field in to; "-1" means to append the field
           to the end.  The second parameter is the key, and the third
           parameter is the value associated with that key.  Since
           fields are distinguished by position, keys may appear more
           than once. */

        m->insertField(-1, "unus", "one");
        m->insertField(-1, "word", "Caesar");
        m->insertField(-1, "unus", "ichi");
        m->insertField(-1, "duo", "two");

        // Send the messages to the "primus" Vobject.  That's it!
        // Simple!

        cout << "vostut3client: sending message...\n";
        primus->sendMessage(&m);


        // Most applications required a run loop which calls
        // flushIncomingBuffers() periodically.  For this simple
        // client we can let the program run to completion.


        // The following exceptions may be emitted by Vobject::findObjectFromRoot():

    } catch(Vobject::NoSuchSiteError e) {
        // The site we wanted to access doesn't exist (we couldn't connect to it)
        cout << "Error!  " << e.what() << "\n";

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

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

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

    } catch(URL::BadURLError e) {
        // We couldn't parse the URL!
        cout << "Error!  " << e.what() << "\n";
    }
}

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