Getting Point cloud data from Openni driver

edit

Previously, I posted how to get started on the point cloud data for the Openni. Many of you posted that i need to get through the tutorials for ROS to have a better understanding. I have done that now.One posted this code(for the subscriber) for me... which was very helpful.I have some qns on this code: 1) We need to have both a publisher and subscriber node for the Kinect in order to get point cloud data.Am i right to say that? 2) how do u get the depth data from the point cloud data?

Really need of help. I am sorry if i ask stupid questions.

    #include <ros/ros.h>
    #include <pcl_ros/point_cloud.h>
    #include <sensor_msgs/PointCloud2.h>

using namespace ros;
using namespace sensor_msgs;

class processPoint {
    NodeHandle nh;
    Subscriber sub;

public:
    processPoint() {
        sub = nh.subscribe<sensor_msgs::PointCloud2>("/camera/rgb/points", 1, &processPoint::processCloud, this);
    }

    ~processPoint() {   
     }

    void processCloud( const sensor_msgs::PointCloud2ConstPtr& cloud );
};

void processPoint::processCloud( const sensor_msgs::PointCloud2ConstPtr& cloud ) {

}

int main(int argc, char **argv) {

    init(argc, argv, "processPoint");

    processPoint processPoint;

    Rate spin_rate(1);

    while( ok() ) {
        spinOnce();

        spin_rate.sleep();
    }
}