ROS Publisher and Subscribers | ROS Noetic Tutorial 2

Design a ROS code for the following Scenario: 

There are two publishers namely Pub1 and Pub2  and there are three subscribers Sub1, sub2 and Sub3.

Pub1 Publishes a topic called \CSE3102 and Sub1 subscribed to it. 

Pub2 publishes a topic called \cse2034 and, sub2, sub3 are subscribed to it. Design a python script for ROS and submit the following details. 

Method of Execution

To begin with, open a terminal and run the following command

$ roscore

Step 1:

Create a folder in the /home/lab21 directory using the command

$ mkdir -p pradeepkumar/src

$ cd pradeepkumar/

$ catkin_make

after the above command, two folders namely build/ and devel/ might have been created.

Now we need to set the PATH for this file devel/setup.bash

One method is to use, the source command when opening a new terminal every time, the

command is

$ source /home/lab21/pradeepkumar/devel/setup.bash

The second method is to include the command in the /home/lab21/.bashrc file, so that the command will

run without any issues when a new terminal is opened.

after the second step, logout and login back in to get the command working and activated else

run the command

$ source .bashrc

Step 2 :

Go to pradeepkumar/src folder and create a catkin package using the following command

$ cd pradeepkumar/src

$ catkin_create_pkg ros_tutorial1 rospy std_msgs

$ cd ..

$ catkin_make

(this time, the make will include the ros_tutorial1 also in to the devel and build libraries)

Step3 - We will be creating two files namely

1. publisher.py

2. subscriber.py

Create the above files in the folder

pradeepkumar/src/ros_tutorial1/script

And give full permission to run

$ chmod 777 *.py

Step 4 - running the publisher and subscriber, we need to open two windows one for pub and another for sub.

In Terminal 1

Go to

$ cd pradeepkumar/

$ source ./devel/setup.bash

$ rosrun ros_tutorial1 pub.py

in Terminal 2

Go to

$ cd pradeepkumar/

$ source ./devel/setup.bash

$ rosrun ros_tutorial1 subs.py

You can see the output of I took ROS Knowledge by the Subscriber and "ROS Knowledge" by the publisher.

$ rqt_graph

will open the graph of all the nodes running under the ROS.

Pub1 code

Publisher 1 

Publisher 2

RQT Graph

Subscriber 1

Subscriber 2

Subscriber 3