Publishing cmd_vel Internally on the TurtleBot3

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On my TurtleBot3's raspberry pi, I hooked it up to a monitor using an HDMI and created a node that publishes a Twist() to /cmd_vel. However, when I publish something such as twist.angular.z = 0.5, this is what rostopic tells me:

leonardo@leonardo:~$ rostopic info /cmd_vel Type: geometry_msgs/Twist

Publishers: * /talker ( http://hidden-ip-number/ )

Subscribers: None

Hypothetically publishing a twist should just make the turtlebot3 move, so I'm unsure what the cause might be. I tried changing the IP of the ROS_MASTER_URI and ROS_HOSTNAME from local to wlan0, but that still gives me the same result above.

Any ideas?