Unable to register with master node [http://3_simulation:11311]: master may not be running yet. Will keep trying

ROSDS Support
1

Please help. I had this error while trying to run the simple_topic_publisher.py in the ROS Basics in 5 days:
Unable to register with master node [http://3_simulation:11311]: master may not be running yet. Will keep trying.

2

Hi @danieladejumo ,

This message appears when there is no roscore running.

roscore is started using the roslaunch command for any valid roslaunch file, or just running in another terminal

roscore

Could you check if you have a roscore, a roslaunch or a simulation running?