Turtlesim Comms: List All Active Nodes

In the following concepts, we will investigate Turtlesimm Comms, and will cover the following steps:

• Listing all active nodes
• Listing all topics
• Getting information about topics
• Showing message information
• Echoing messages in real-time

Now that we’ve launched turtlesim_node, and played around with sending commands via the turtle_teleop_key node, let’s dig deeper, to see what’s actually happening underneath the surface…

Listing all Active Nodes

To get a list of all nodes that are active and have been registered with the ROS Master, we can use the command rosnode list. Let’s do so now:

We can see that there are three active nodes that have been registered with the ROS Master, /rosout, /teleop_turtle, and /turtlesim.

• /rosout
  This node is launched by roscore. It subscribes to the standard /rosout topic, the topic to which all nodes send log messages.
• /teleop_turtle
  This is our keyboard teleop node. Notice that it’s not named turtle_teleop_key. There’s no requirement that a node’s broadcasted name is the same as the name of it’s associated executable.
• /turtlesim
  The node name associated with the turtlebot_sim node