# [rwt_moveit] datatype/md5sum error

Hello everyone,

I'm trying to use rwt_moveit package alongside with cyton_gamma_300 moveit package on ROS Melodic. I can visualize the robot and the markers on the web page, but as soon I launch the /moveit_publisher node I get this error:

Client [/moveit_publisher] wants topic /move_group/result to have datatype/md5sum [moveit_msgs/MoveGroupActionResult/47ef72f231e49f6059f185fc18418665], but our version has [moveit_msgs/MoveGroupActionResult/6ee8682a508d60603228accdc4a2b30b]. Dropping connection.

So according to what I found in the community, this error occurs when two nodes try to communicate with each other, but from two different ROS environments (like one node from Indigo, and the other one from Kinetic). But in my case, all nodes are in the same ROS environment which is Melodic.

Here is the launch file:

<launch> <arg name="fixed_frame" default="/world"/> <arg name="is_sim" default="false"/>

<param name="fixed_frame" value="$(arg fixed_frame)" /> <param name="sim_mode" value="$(arg is_sim)" />

<include file="$(find cyton_gamma_300_moveit_config)/launch/demo.launch"/> <include file="$(find rosbridge_server)/launch/rosbridge_websocket.launch" />

<node pkg="tf" type="static_transform_publisher" name="connect_start" args="0 0 0 0 0 0 $(arg fixed_frame) /start$(arg fixed_frame) 100" />

<node pkg="tf" type="static_transform_publisher" name="connect_goal" args="0 0 0 0 0 0 $(arg fixed_frame) /goal$(arg fixed_frame) 100" />

<!--node name="tf_web_republisher" pkg="py_tf2_web" type="tf_web_republisher.py" /-->
<node name="tf2_web_republisher" pkg="tf2_web_republisher" type="tf2_web_republisher" />

<node pkg="robot_state_publisher" type="robot_state_publisher" name="start_state_publisher_start">
<remap from="joint_states" to="start_joint_states" />
<param name="tf_prefix" type="string" value="start" />
</node>
<node pkg="robot_state_publisher" type="robot_state_publisher" name="goal_state_publisher_goal">
<remap from="joint_states" to="goal_joint_states" />
<param name="tf_prefix" type="string" value="goal" />
</node>


</launch>

Here are the info about the /move_group/result topic:

rostopic info /move_group/result Type: moveit_msgs/MoveGroupActionResult

Publishers: * /move_group (http://laresi-MS-7978:41113/)

Subscribers: * /moveit_publisher (http://laresi-MS-7978:38973/) * /rviz_laresi_MS_7978_6064_4036308910317907203 (http://laresi-MS-7978:43175/)

Can anyone, please, give me some advice or a clue? Thank you very much!

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This error also occurs if one of your nodes refers to an older message definition than the other. Try cleaning and rebuilding your workspace ( catkin clean -y && catkin build ) and sourcing it in all the terminals ( source devel/setup.bash ). The latter step is important.

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Thank you for your answer . After looking up into the moveit_msgs package, I found out that msgs definitions are different from the source. Actually, I have installed ros-melodic-moveit-msgs from the repos, the package installed in /opt/ros/melodic/... path does contain moveit_msgs/MoveGroupActionResult message, which is not the case if you look into the source code on GitHub https://github.com/ros-planning/movei... on Melodic branch. I was not able to install the package from source, because of some errors in building other dependencies. I wonder why the two versions are so different, eventhough they are both for Melodic?

( 2020-11-10 09:16:46 -0600 )edit

.action files are generated into RequestResult and Feedback messages, so the message you see is based on this action. It would look the same if you built it locally. You can also build moveit from source if this doesn't work.

( 2020-11-10 11:17:40 -0600 )edit

I have cleaned and rebuiled my workspace, and have builed moveit from source as showed in the tutorial. Now everything is working just fine! Thank you very much fvd

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