Topics: Channels for Data Exchange
A topic in ROS is a named bus over which nodes exchange messages. Topics are primarily used for asynchronous communication between nodes, where data producers (publishers) and consumers (subscribers) do not need to know about each other’s presence.
Key Characteristics of Topics:
- Named Communication Channels: Topics have unique names, like /camera/image or /cmd_vel, representing specific types of data.
- Asynchronous Messaging: Topics allow publishers and subscribers to work independently. A node can publish data to a topic whenever it's ready, and other nodes can subscribe to receive the data when needed.
- Many-to-Many Communication: A single topic can have multiple publishers and subscribers, enabling flexible communication between nodes.
Example
- Sensor Topics: For example, /scan might carry laser scan data from a LIDAR sensor.
- Control Topics: /cmd_vel can carry velocity commands for controlling the robot’s movement.