Simple ROS Publisher Subscriber with simple ROS Service

This is a simple example to run publisher and subscriber with ros service in ROS Melodic.

Functionalities

• Simple ROS publisher-subscriber
• Simple ROS Service
• TF Broadcaster
• Gtest and ROSTest
• rosbag

Dependencies

• Ubuntu 18.04 (LTS)
• ROS Melodic

Instructions to build and run the code

• Make sure you have ROS Melodic installed in your computer. If not refer to site.

• Create a workspace:

  mkdir -p ~/pubsub_ws/src
  cd ~/pubsub_ws/src
  

• Clone the repository into the workspace:

  git clone https://github.com/anubhavparas/beginner_tutorials.git
  

• Build the workspace:

  cd ~/pubsub_ws
  catkin_make or catkin build (preferred)
  source devel/setup.bash
  

Running with the launch file

• Run using launch file: This will spawn:

  • a ros service node: /anubhavp/modify_string_service
  • a publisher node: /anubhavp/talker
  • a subscriber node: /anubhavp/listener

  roslaunch beginner_tutorials beginner_tutorials.launch buffer_size:=1 loop_rate:=10
  
  # arguments are:
  # buffer_size - default=1
  # loop_rate - default=10
  # is_record_bag - default=false
  # bagfile - default=recorded_topics.bag
  

• To enable rosbag recording. By default it is disabled.

  • This will store the rosbag recording in a file home/<username>/.ros/recorded_topics.bag

    roslaunch beginner_tutorials beginner_tutorials.launch is_record_bag:=true
    

• To call the service:

  rosservice call /anubhavp/modify_string_service "inputstring: 'Let us learn ROS.'"
  

• /talker node also broadcasts tf frame information from /world to /talk frame. Example.

  • To check the frame information run

    rosrun tf tf_echo world talk
    

  • For visualizing the tree of frames being broadcasted over ROS. Example.

    rosrun rqt_tf_tree rqt_tf_tree 
    

  • view_frames creates a diagram of the frames being broadcast by tf over ROS. Example.

     rosrun tf view_frames
    

Running without the launch file

• Start ros master node in a separate terminal:

  roscore
  

• To run the service run the following in a new terminal:

  cd ~/pubsub_ws/
  source devel/setup.bash
  rosrun beginner_tutorials modify_string_service
  

• To run the publisher run the following in a new terminal:

  cd ~/pubsub_ws/
  source devel/setup.bash
  rosrun beginner_tutorials talker 1 10
  

• To run the subscriber run the following in a new terminal:

  cd ~/pubsub_ws/
  source devel/setup.bash
  rosrun beginner_tutorials listener
  

• To call the service:

  rosservice call /modify_string_service "inputstring: 'Let us learn ROS.'"
  

Rosbag record and play

• To run rosbag recording run the following in a new terminal (assuming the above nodes are running):

  cd ~/pubsub_ws/
  source devel/setup.bash
  rosbag record -O record_topics.bag -a --duration 15
  
  # -a: to record all topics
  # -O record_topics.bag: name of the output bag file
  # --duration 15: record for 15 sec 
  

• To verify the recording:

  • Examining the bag file:

    rosbag info <your bagfile>
    

  • Stop the /talker node and only start the listner node

    cd ~/pubsub_ws/
    source devel/setup.bash
    rosrun beginner_tutorials listener
    

  • Replay the bag file:

    rosbag play record_topics.bag
    

  • You can verify that the listener is now subscribing to the recorded messages.

• Run a sample recorded rosbag file.

  • In a new terminal start rosmaster:

    roscore
    

  • In a new terminal start the listner of the /chatter topic:

    cd ~/pubsub_ws/
    source devel/setup.bash
    rosrun beginner_tutorials listener
    

  • In a new terminal replay the bag file. This is a 15 sec recording of many topics including /chatter topic.

    cd ~/pubsub_ws/
    source devel/setup.bash
    roscd beginner_tutorials
    cd results/bag
    

  • Examining the bag file: Sample output.

    rosbag info record_topics.bag
    

  • Play the bag file: Sample output.

    rosbag play record_topics.bag
    

Running the tests

• Build the test:

  cd ~/pubsub_ws/
  catkin_make
  catkin_make run_tests (to run all the test executables)
  (or)
  catkin_make run_tests talker_test (to run specific executable)
  

• tests can be run using rostest too, once $catkin_make run_tests have been run once.

  source devel/setup.bash
  rostest beginner_tutorials publisher_test.test