# ROS Interface start and stop signals on executing commands

**URL:** <https://forum.hello-robot.com/t/ros-interface-start-and-stop-signals-on-executing-commands/417>\
**Category:** Ask\
**Created:** [June 1, 2022, 3:51pm UTC](https://forum.hello-robot.com/t/ros-interface-start-and-stop-signals-on-executing-commands/417 "2022-06-01T15:51:26Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![smth](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/smth/32/94_2.png) [@smth](https://forum.hello-robot.com/u/smth)\
**Post date:** [June 1, 2022, 3:51pm UTC](https://forum.hello-robot.com/t/ros-interface-start-and-stop-signals-on-executing-commands/417/1 "2022-06-01T15:51:26Z")

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@binitshah we discussed this when we met a couple of weeks ago.

You mentioned that once I issue a move command via the ROS interface, there is a particular ROS topic that starts sending messages, and once the move command finishes executing, it stops sending messages.  
Can you provide the details – which topic is it, etc.?

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**Author:** ![bshah](https://yyz2.discourse-cdn.com/flex030/user_avatar/forum.hello-robot.com/bshah/32/55_2.png) [@bshah](https://forum.hello-robot.com/u/bshah)\
**Post date:** [June 1, 2022, 5:22pm UTC](https://forum.hello-robot.com/t/ros-interface-start-and-stop-signals-on-executing-commands/417/2 "2022-06-01T17:22:55Z")

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Yes, it’s called the `/stretch_controller/follow_joint_trajectory/feedback` topic and it’s part of the follow\_joint\_trajectory action server. This topic will publish feedback messages when any of the robot’s joints are in motion.

The follow\_joint\_trajectory action server is comprised of 5 topics. To command the robot’s joints into motion, the goal topic is used.

```auto
$ rostopic list
[...]
/stretch_controller/follow_joint_trajectory/cancel
/stretch_controller/follow_joint_trajectory/feedback
/stretch_controller/follow_joint_trajectory/goal
/stretch_controller/follow_joint_trajectory/result
/stretch_controller/follow_joint_trajectory/status

```

The follow\_joint\_trajectory action server is implemented in [this file](https://github.com/hello-robot/stretch_ros/blob/dev/noetic/stretch_core/nodes/joint_trajectory_server.py) and is part of the [stretch\_driver node](https://github.com/hello-robot/stretch_ros/blob/dev/noetic/stretch_core/nodes/stretch_driver) from Stretch Core. Launching the node will give you access to the 5 topics. Here’s the launch command:

```nohighlight
roslaunch stretch_core stretch_driver.launch

```