ROS2 Simple Publisher

🧠 Concept: Publishers and Topics

In ROS2, nodes communicate through topics — named data channels.

A publisher sends data onto a topic. A subscriber receives it. They never talk directly — the topic sits between them:

[your node] ──publishes──▶ /chatter ──receives──▶ [any subscriber]

Key API:

self.pub = self.create_publisher(MessageType, '/topic_name', queue_depth)

• MessageType — the kind of data (String, Int32, LaserScan…)
• '/topic_name' — the channel name, always starts with /
• queue_depth — buffer size if subscriber is slow. Use 10 as default.

To publish at a fixed rate, pair with a timer:

self.timer = self.create_timer(1.0, self.callback)  # fires every 1.0 second

Problem Statement

Create a ROS2 Python node that continually publishes a string message to a topic. This is the "Hello World" of ROS2.

Requirements

• Node name: simple_publisher
• Topic: /chatter
• Message type: std_msgs/String
• Rate: 1 Hz (once per second)
• Content: "Hello ROS2!"

Input/Output Format

Input: None | Output: /chatter (std_msgs/String)

⚠️ Common Pitfalls

• Forgetting to spin the node
• Wrong topic name

📚 Helpful Resources

• ROS2 Concept: Simple Publisher