error while building after adding a Subscriber node

edit

I created a subscriber node "Listener.cpp" in the src folder of the package ardrone_autonomy.

I also modified the CMakeLists.txt file by adding dependency, executable link However, when I go to my catkin workspace and type in "catkin_make",

It builds fine except for something wrong with my new file. What am I missing/ doing wrong?

ERROR shown below:

...
...
[100%] Building CXX object ardrone_autonomy/CMakeFiles/ardrone_driver.dir/src/listener.cpp.o
Linking CXX executable /home/voladoddi/catkin_ws/devel/lib/ardrone_autonomy/ardrone_driver
CMakeFiles/ardrone_driver.dir/src/listener.cpp.o: In function `main':
listener.cpp:(.text+0x152): multiple definition of `main'
CMakeFiles/ardrone_driver.dir/src/ardrone_driver.cpp.o:ardrone_driver.cpp:(.text+0x16a61): first defined here
/usr/bin/ld: cannot find -llistener
collect2: ld returned 1 exit status
make[2]: *** [/home/voladoddi/catkin_ws/devel/lib/ardrone_autonomy/ardrone_driver] Error 1
make[1]: *** [ardrone_autonomy/CMakeFiles/ardrone_driver.dir/all] Error 2
make: *** [all] Error 2
Invoking "make" failed

I checked the .cpp file I wrote. I cannot see any multiple definitions of main in the file. There's no other subscriber node named the same way either.

EDIT - As William pointed out, I was trying add the node to the executable of the existing package. However, I added two lines to the end of my Subscriber.cpp file like below:

#adding subscriber's node executable to the end of CMakeLists.txt file - POOJA
add_executable(subscriber src/subscriber.cpp)
target_link_libraries(subscriber ${catkin_LIBRARIES})

And now I'm getting the following errors:

 Build done.
Checking required Ubuntu packages ...
/home/voladoddi/catkin_ws/src/ardrone_autonomy/src/subscriber.cpp: In function ‘void ReceiveData(const ConstPtr&)’:
/home/voladoddi/catkin_ws/src/ardrone_autonomy/src/subscriber.cpp:8:2: error: ‘const struct ardrone_autonomy::Navdata_<std::allocator<void> >’ has no member named ‘data’
/home/voladoddi/catkin_ws/src/ardrone_autonomy/src/subscriber.cpp: In function ‘int main(int, char**)’:
/home/voladoddi/catkin_ws/src/ardrone_autonomy/src/subscriber.cpp:17:54: error: ‘Navdata’ was not declared in this scope
/home/voladoddi/catkin_ws/src/ardrone_autonomy/src/subscriber.cpp:17:54: note: suggested alternative:
/home/voladoddi/catkin_ws/devel/include/ardrone_autonomy/Navdata.h:246:61: note:   ‘ardrone_autonomy::Navdata’
ok.
Building ARDroneTool/Lib
make[2]: *** [ardrone_autonomy/CMakeFiles/subscriber.dir/src/subscriber.cpp.o] Error 1
make[1]: *** [ardrone_autonomy/CMakeFiles/subscriber.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....
Building ARDroneTool/Lib
[  4%] Performing install step for 'ardronelib'
make[3]: warning: jobserver unavailable: using -j1.  Add `+' to parent make rule.
[  5%] Completed 'ardronelib'
[  7%] Built target ardronelib
make: *** [all] Error 2

Here is my subscriber code:

#include "ros/ros.h"
#include "ardrone_autonomy/Navdata.h"

//The topics subscribed to : Time (from the header), Pitch angle(rotY)
// where the MESSAGE= ardrone_autonomy
void ReceiveData(const ardrone_autonomy::Navdata::ConstPtr& rot)
{
    ROS_INFO("Time: %d, Pitch angle: %d",rot->data.header.stamp.to_sec(),rot->rotY);
}


//instantiating subscriber
int main(int argc, char **argv)
{
    ros::init(argc,argv,"subscriber");
    ros::NodeHandle n;
    ros::Subscriber sub = n.subscribe("ardrone/navdata",Navdata,ReceiveData);
    ros::spin();

    return 0;
}