why my listener can't get the published data?

edit

Dear friends: I have built two nodes :main and listener. The main nead to read (x,y,z) from a device and publish to the listener. The main code can read the data but the listener can't get the published data now,and i even don't know whether the publish is success,how should i handle it? Thanks for you help. The result of rosrun talker: X=0.013095 Y=-0.0524488 Z=-0.0401042

But the listener is like this: X: 0 Y: 0 Z: 0

The rosmsg show is: dong@dong-H61MHB:~/Project/robot_test$ rosmsg show rosfalcon/falconPos float64 X float64 Y float64 Z The source code of publisher

int main(int argc, char* argv[]) 
   { ros::init(argc,argv, "main");
    if(init_falcon(0))
    { 
        std::cout << "Falcon Initialised Starting ROS Node" <<std::endl;
       m_falconDevice.setFalconKinematic<libnifalcon::FalconKinematicStamper>();
       ros::NodeHandle node;
       ros::Publisher pub = node.advertise<rosfalcon::falconPos>("falconPos",10);
while(node.ok())
     {       boost::array<double, 3> Pos;
            Pos = m_falconDevice.getPosition();
            rosfalcon::falconPos position;
            position.X = Pos[0];
            position.Y = Pos[1];
            position.Z = Pos[2];
            pub.publish(position);
            std::cout << "X="<< position.X<< "  Y="<< position.Y<< "
Z="<< position.Z << std::endl;      
            }
        m_falconDevice.close();
    }   return 0;
    }

And the main part of listener is:

int main(int argc, char *argv[])
{
  ros::init(argc, argv, "listener");
  ros::NodeHandle node;
while(node.ok())
{
  ros::Subscriber sub = node.subscribe("position", 10,&positionCallback);
}
  ros::spin();
  return 0;
}