apps/tutorials/vostut3server.cc

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

   This tutorial file covers:
   - Telling to VOS sleep when waiting for network input
   - Enabling message queuing on Vobjects
   - Retrieving queued messages
   - Accessing message fields

   This file (vostut3server.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 before running vostut3client.

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

    LocalSocketSite localsite(&NoAccessControl::static_);

    /*  By default, when flushIncomingBuffers() is called it will
        check to see if there is any pending data from the network,
        act on that data and return.  If there is no waiting data, it
        will return immediately.  For a server application which
        spends most of its time waiting for requests this behavior is
        bad; it will waste CPU cycles by constantly checking to see if
        there is any new data.  Using setTimeoutOnSelect you can set a
        wait timeout for flushIncomingBuffers().  This means that
        flushIncomingBuffers() will sleep either until there is some
        network data to process or until this number of seconds has
        elapsed.  During this time the process will be put to sleep by
        the operating system and not using any CPU time.  If the
        timeout is -1, it will sleep indefinitely until there is some
        network activity. */

    localsite.setTimeoutOnSelect(-1);

    /* The Vobject API is an abstract class which works for both local
       and remote Vobjects (more on this in vostut3client.cc) Here we
       will use a C++ cast to convert it into a slightly more concrete
       class so that we can access a certain method.  A local site
       creates local Vobjects, obviously :-) */

    vRef<LocalVobject> primus
        = dynamic_cast<LocalVobject*>(localsite.createMetaObject("primus", 0));

    /* There are three ways of handling incoming messages in your
     application: you can extend the Vobject and override the
     sendMessage() method, you can use addMessageHandler() to set up a
     callback or you can enable message queuing (disabled by default)
     and call receiveMessage() to retrieve queued messages.  This
     tutorial demonstrates the third way, but the first two are
     generally preferred and are discussed in later tutorials. */

    primus->setQueueMsgs(true);

    cout << "vostut3server: Vobject site name is: " << primus->getName() << "\n";
    cout << "vostut3server: Vobject URL is: " << primus->getURL().getString() << "\n";
    vRef<Site> site = primus->getSite();
    cout << "vostut3server: Vobject site is: " << site->getURL().getString() << "\n";
    cout << "vostut3server: Our local site is: " << localsite.getURL().getString() << "\n";

    // The difference between local and remote objects is discussed in
    // vostut3client.
    cout << "vostut3server: Primus is local? " << primus->isLocal() << "\n";
    cout << "vostut3server: Primus is remote? " << primus->isRemote() << "\n";

    // Our run loop has been expanded: it will now print out any
    // messages received by our "primus" object
    while(true) {

        // This will sleep until something happens, at which point it
        // will wake up, parse the inbound message to create a Message
        // object, queue the message and return.
        localsite.flushIncomingBuffers();

        // This loop prints out any queued messages
        while(primus->hasMessageAvailable()) {

            // Get the next message that primus has received, removing
            // the message from the queue. Note that the Message class
            // is reference counted.
            vRef<Message> msg = primus->receiveMessage();

            // First print out the message
            cout << "vostut3server: " << primus->getName() << " received a message:\n" << msg->getLoggableString() << "\n";

            // Messages have a number of standard fields.  The "method"
            // field indicates the action the sender is expressing.
            if(msg->getMethod() == "tutorial:hello") {

                // Another standard field is "from".  There is of
                // course a "to" field as well :-)
                cout << "vostut3server: " << msg->getFrom() << " said hello to us!  Isn't that nice.\n";

                try {
                    /* We can access a particular field using its
                       name.  If no field by that name is present,
                       then a Message::NoSuchFieldError exception will
                       be thrown.  You cannot access the fixed to,
                       from, method, etc fields this way (use getTo(),
                       getFrom(), getMethod() instead). */

                    cout << "vostut3server: The word of the day is \"" << msg->getField("word").value << "\"\n";

                } catch(Message::NoSuchFieldError) {
                    // If we ask for a certain field on a message and it is not present,
                    // this exception will be thrown
                    cout << "vostut3server: Oops, no \"word\" field is present, no word of the day for us.\n";
                }

                cout << "vostut3server: The fields in this message are:\n";

                // The fields in a message are ordered and so it is
                // possible to iterate over them.
                for(int i = 0; i < msg->getNumFields(); i++) {
                    cout << "  " << msg->getField(i).key << "=\"" << msg->getField(i).value << "\"\n";
                }
            }
        }
    }
}

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