roscore rosrun turtlesim turtlesim_node rosrun turtlesim turtle_teleop_key
——————————————
| ROS Master |
——————————————
||
\/
____________________________
|| ||
\/ \/
____________ message ____________ | 发布者 |————————————>| 订阅者 | ———————————— ———————————— || || / ____________ / ———————>| topic |<————— ————————————