ROS 2 Quick Start: Your First Node in 5 Minutes

If you're new to robotics, ROS 2 (Robot Operating System 2) might seem intimidating. But creating your first node is surprisingly simple! Let's build a "Hello World" publisher-subscriber system.

Prerequisites

• Ubuntu 22.04 (or Docker)
• ROS 2 Humble installed
• Python 3.10+

# Quick install (if needed)
sudo apt install ros-humble-desktop python3-colcon-common-extensions
source /opt/ros/humble/setup.bash

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Step 1: Create a Workspace

mkdir -p ~/ros2_ws/src
cd ~/ros2_ws/src

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Step 2: Create a Package

ros2 pkg create --build-type ament_python hello_ros2 --dependencies rclpy std_msgs

This creates:

hello_ros2/
├── package.xml
├── setup.py
├── hello_ros2/
│   └── __init__.py

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Step 3: Write the Publisher Node

Create hello_ros2/publisher.py:

import rclpy
from rclpy.node import Node
from std_msgs.msg import String

class HelloPublisher(Node):
    def __init__(self):
        super().__init__('hello_publisher')
        self.publisher = self.create_publisher(String, 'greetings', 10)
        self.timer = self.create_timer(1.0, self.publish_message)
        self.counter = 0
    
    def publish_message(self):
        msg = String()
        msg.data = f'Hello, ROS 2! Message #{self.counter}'
        self.publisher.publish(msg)
        self.get_logger().info(f'Published: "{msg.data}"')
        self.counter += 1

def main(args=None):
    rclpy.init(args=args)
    node = HelloPublisher()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

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Step 4: Write the Subscriber Node

Create hello_ros2/subscriber.py:

import rclpy
from rclpy.node import Node
from std_msgs.msg import String

class HelloSubscriber(Node):
    def __init__(self):
        super().__init__('hello_subscriber')
        self.subscription = self.create_subscription(
            String,
            'greetings',
            self.listener_callback,
            10
        )
    
    def listener_callback(self, msg):
        self.get_logger().info(f'Received: "{msg.data}"')

def main(args=None):
    rclpy.init(args=args)
    node = HelloSubscriber()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

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Step 5: Register Entry Points

Edit setup.py:

entry_points={
    'console_scripts': [
        'publisher = hello_ros2.publisher:main',
        'subscriber = hello_ros2.subscriber:main',
    ],
},

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Step 6: Build and Run

cd ~/ros2_ws
colcon build --packages-select hello_ros2
source install/setup.bash

Terminal 1:

ros2 run hello_ros2 publisher

Terminal 2:

ros2 run hello_ros2 subscriber

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Output

Publisher:

[INFO] [hello_publisher]: Published: "Hello, ROS 2! Message #0"
[INFO] [hello_publisher]: Published: "Hello, ROS 2! Message #1"

Subscriber:

[INFO] [hello_subscriber]: Received: "Hello, ROS 2! Message #0"
[INFO] [hello_subscriber]: Received: "Hello, ROS 2! Message #1"

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What Just Happened?

1. Publisher Node sends messages to the /greetings topic every second
2. Subscriber Node listens to /greetings and logs received messages
3. ROS 2 middleware handles all the networking magic behind the scenes

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Next Steps

• Add parameters (e.g., message frequency)
• Create custom message types
• Visualize with rqt_graph

🎉 Congratulations! You've just built your first ROS 2 system. From here, you can control real robots, integrate sensors, and build autonomous behaviors.

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Full Code: GitHub Repo
Next Tutorial: Service Calls and Action Servers
Author: Muhammed Ibrahim