If you are working with two different machines, for example: Erle-Brain and your laptop remember to configure ROS_MASTER_URI and ROS_IP. Maybe could be interesting to put this lines in your ~/.bashrc, it is necessary to have ROS installed in both machines.
export ROS_MASTER_URI=http://10.0.0.1:11311 export ROS_IP=10.0.0.1
Laptop or PC:
export ROS_MASTER_URI=http://10.0.0.1:11311 export ROS_IP=10.0.0.2 sudo bash -c 'echo -e "10.0.0.1\terle-brain" > /etc/hosts'