Start the master
ssh hal roscore
Start the listener
ssh hal export ROS_MASTER_URI=http://hal:11311 rosrun rospy_tutorials listener.py
Start the talker
ssh marvin export ROS_MASTER_URI=http://hal:11311 rosrun rospy_tutorials talker.py
rostopic
rostopic list # You get a list of all available topics rostopic echo /topic_name # check if there is a connection and messages still come.
When something goes wrong
echo $ROS_IP