Hands-On ROS for Robotics Programming

Combining the publisher and subscriber in the same node

Can a node talk and listen at the same time as a real human does? Well, if ROS is a framework for robotics, it should be possible. Let's explore this:

1. Launch these two commands in the first two terminals, with each one in an independent terminal:

T1 $ roscoreT2 $ rosrun ros_basics doubler.py

/doubler is a node that subscribes to the /number topic, as specified in these two lines of the doubler.py script:

rospy.init_node('doubler')...sub = rospy.Subscriber('number', Int32, callback)...

Additionally, /doubler publishes its result in the /doubled topic:

...pub = rospy.Publisher('doubled', Int32, queue_size=10)

You will notice that nothing happens, because it needs to be fed with a number ...