DDS Talk/Listen Example

The talkListenDds example is two separate applications: one which publishes a simple DDS entity, and one which listens for published DDS entities.

This is a standalone example that can be run independently from VR-Exchange, and serves to illustrate the procedures involved in publishing and reflecting DDS objects. These applications can be used in conjuction with the DDS broker for testing or development.

• talk.cxx
• listen.cxx

---

talk.cxx

/****************************************************************************
 * Copyright (c) 2016 MAK Technologies, Inc.
 * All rights reserved.
 ****************************************************************************/


#include <vlDds/ddsDomainConnection.h>
#include <vlDds/ddsDomainConnectionInitializer.h>
#include <vlDds/entityPublisher.h>

#include <vl/entityStateRepository.h>
#include <vl/topoView.h>

#include <vlutil/vlProcessControl.h>
#include <vlutil/vlMiniDumper.h>
#include <vlutil/vlKeyboard.h>

#include <iostream>

void updateLocationOrientation( DtTime t, DtTopoView& view );

using namespace MAKVrExchange::DtDdsBroker;

int main( int argc, char* argv[] )
{
   DtINIT_MINIDUMPER( "DDS Talk" );

   try
   {
      // Get the partition name from the command line.
      DtString partitionName = "VR-Exchange";
      if ( argc > 1 )
      {
         partitionName = argv[1];
      }

      // Set the partition name in the initializer.
      DtDdsDomainConnInitializer appInit;
      appInit.setPartitionName( partitionName );

      // The DtExerciseConn instance is perhaps the most important class
      // in any VR-Link exercise. Think of it as the hub which holds
      // everything else together. Technically this instance is what's
      // responsible for connecting this federate to another federate via
      // a network, or an RTI. After exConn is created, and if no error
      // has occurred this simulator will be a live federate.
      DtDdsDomainConnection exConn( appInit );

      // Initialize VR-Link time.
      DtClock* clock = exConn.clock();

      // Entity type.
      DtEntityType type( "1:2:225:50:4:1:0" );

      // Instantiate an entity publisher.
      DtEntityPublisher publisher( &exConn, "Predator_UAV" );
      DtEntityStateRepository* entSr = publisher.esr();
      entSr->setGlobalId( DtEntityIdentifier(1,2,3) );
      entSr->setEntityId( DtEntityIdentifier(1,2,3) );
      entSr->setMarkingText( "Predator_UAV" );
      entSr->setForceId( DtForceFriendly );
      entSr->setEntityType( type );
      entSr->setGuise( type );

      // Create a topo view for updating the entity's location, and initialize it.
      DtTopoView topoView( entSr, DtDeg2Rad(35.699760), DtDeg2Rad(-121.326577) );
      updateLocationOrientation( clock->elapsedRealTime(), topoView );

      while ( true )
      {
         // Check if user hit 'q' to quit.
         char* keyPtr = DtPollBlockingInputLine();
         if ( keyPtr && ( *keyPtr == 'q' || *keyPtr == 'Q' ) )
         {
            break;
         }

         // Tell VR-Link the current value of simulation time.
         clock->setSimTime( clock->elapsedRealTime() );


         // Update the aircraft's location and orientation.
         updateLocationOrientation( clock->elapsedRealTime(), topoView );

         // Process any incoming messages.
         exConn.drainInput();

         // Tick the publisher.
         publisher.tick();

         // Sleep till next iteration.
         DtSleep( 0.1 );
      }
   }
   DtCATCH_AND_WARN( std::cout );
   return 0;
}

void updateLocationOrientation( DtTime t, DtTopoView& view )
{
   // Orbit constants.
   const float radius = 200;                 // Radius of the orbit.
   const float period = 20.0;                // Time to do a full orbit.
   const float speed = M_2PI*radius/period;  // Approx speed the aircraft is moving.

   // Intermediate variables.
   float angle = t*M_2PI/period;    // Angle around orbit.
   float advAngle = angle + M_PI_2; // Angle + Pi/2 around orbit.

   // Update the location/velocity/orientation.
   view.setLocation( DtVector64(200*cos(angle),-200*sin(angle),-1230.0) );
   view.setVelocity( DtVector32(speed*cos(advAngle),speed*sin(advAngle),-1230.0) );
   view.setOrientation( DtTaitBryan(-advAngle,0,DtDeg2Rad(-15)) );
}

---

listen.cxx

/****************************************************************************
 * Copyright (c) 2016 MAK Technologies, Inc.
 * All rights reserved.
 ****************************************************************************/


#include <vlDds/reflectedEntity.h>
#include <vlDds/ddsDomainConnectionInitializer.h>
#include <vlDds/ddsDomainConnection.h>

#include <vl/entityStateRepository.h>

#include <vlutil/vlProcessControl.h>
#include <vlutil/vlMiniDumper.h>
#include <vlutil/vlKeyboard.h>

#include <iostream>

using namespace MAKVrExchange::DtDdsBroker;

void discoverObject( void* refObj, void* /*usr*/ );
void updateObject( void* refObj, void* /*usr*/ );
void removeObject( void* refObj, void* /*usr*/ );

int main( int argc, char* argv[] )
{
   DtINIT_MINIDUMPER( "DDS Listen" );

   try
   {
      // Get the partition name from the command line.
      DtString partitionName = "VR-Exchange";
      if ( argc > 1 )
      {
         partitionName = argv[1];
      }

      // Set the partition name in the initializer.
      DtDdsDomainConnInitializer appInit;
      appInit.setPartitionName( partitionName );

      // The DtExerciseConn instance is perhaps the most important class
      // in any VR-Link exercise. Think of it as the hub which holds
      // everything else together. Technically this instance is what's
      // responsible for connecting this federate to another federate via
      // a network, or an RTI. After exConn is created, and if no error
      // has occurred this simulator will be a live federate.
      DtDdsDomainConnection exConn( appInit );

      // Subscribe for object discovery and removal.
      exConn.addEntityAdditionCallback( discoverObject, 0 );
      exConn.addEntityRemovalCallback( removeObject, 0 );

      // Initialize VR-Link time.
      DtClock* clock = exConn.clock();

      while ( true )
      {
         // Check if user hit 'q' to quit.
         char* keyPtr = DtPollBlockingInputLine();
         if ( keyPtr && ( *keyPtr == 'q' || *keyPtr == 'Q' ) )
         {
            break;
         }

         // Tell VR-Link the current value of simulation time.
         clock->setSimTime( clock->elapsedRealTime() );

         // Process any incoming messages.
         exConn.drainInput();

         // Sleep till next iteration.
         DtSleep( 0.1 );
      }
   }
   DtCATCH_AND_WARN( std::cout );
   return 0;
}

void discoverObject( void* refObj, void* /*usr*/ )
{
   DtReflectedEntity* entity = (DtReflectedEntity*) refObj;
   std::cout << "Discovered new Entity:" << std::endl;
   std::cout << *entity->esr() << std::endl;
   std::cout << std::endl;

   // Subscribe to further updates to the object.
   entity->addPostUpdateCallback( updateObject, 0 );
}

void updateObject( void* refObj, void* /*usr*/ )
{
   DtReflectedEntity* entity = (DtReflectedEntity*) refObj;
   std::cout << "Received Entity Update:" << std::endl;
   std::cout << *entity->esr() << std::endl;
   std::cout << std::endl;
}

void removeObject( void* refObj, void* /*usr*/ )
{
   DtReflectedEntity* entity = (DtReflectedEntity*) refObj;
   std::cout << "Entity Removed:" << std::endl;
   std::cout << *entity->esr() << std::endl;
   std::cout << std::endl;
}