You will typically see this error on Mac OS. This is because the default ROS master is not set to localhost. To fix this, you need to run following lines to in your terminal.
export ROS_HOSTNAME=localhost
export ROS_MASTER_URI=http://localhost:11311
export ROS_IP=localhost
We also provide a script to automate this process. Simply run source local_ros.sh in your terminal.
Important: You need to run these lines every time you open a new terminal. Or, you can export them to your shell profile by running
proile= # choose from ~/.bash_profile, ~/.zshrc, and ~/.bashrc
echo "export ROS_HOSTNAME=localhost" >> $profile
echo "export ROS_MASTER_URI=http://localhost:11311" >> $profile
echo "export ROS_IP=localhost" >> $profile
This is a common error on Mac OS. To fix this, you need to install the Xcode Command Line Tools. You can do this by running the following command in your terminal.
xcode-select --install
Very likely, you forgot to run source devel/setup.bash in your workspace.
Do not panic, let's just try to delete the ROS environment and reinstall it.
First, go back to the base environment.
conda activate base
Then, delete the ROS environment.
conda env remove -n ros_base
Finally, reinstall ROS following this tutorial.