# Topics Mini Project LaserScan library confusion

**URL:** <https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965>\
**Category:** ROS2 In 5 Days Python\
**Created:** [June 8, 2020, 2:52pm UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965 "2020-06-08T14:52:15Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![t.alscher](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/t.alscher/32/10_2.png) [@t.alscher](https://get-help.theconstruct.ai/u/t.alscher)\
**Post date:** [June 8, 2020, 2:52pm UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/1 "2020-06-08T14:52:15Z")

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Hi,

I have a problem with the mini project. I can’t include “sensor\_msgs/msg/laserscan.hpp” (no such file or directory). I also tried: sensor\_msgs/msg/LaserScan.hpp, sensor\_msgs/LaserScan.hpp and like in ros1 sensor\_msgs/laserscan.h  
The /kobuki/laser/scan topic doesn’t have a subscriber or publisher if I make ros2 topic info on it (the bridge is running).

best regards

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**Author:** ![bayodesegun](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/bayodesegun/32/6966_2.png) [@bayodesegun](https://get-help.theconstruct.ai/u/bayodesegun)\
**Post date:** [June 9, 2020, 11:13am UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/2 "2020-06-09T11:13:29Z")

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Hi @t.alscher,

> [@t.alscher](#):
>
> I have a problem with the mini project. I can’t include “sensor\_msgs/msg/laserscan.hpp” (no such file or directory). I also tried: sensor\_msgs/msg/LaserScan.hpp, sensor\_msgs/LaserScan.hpp and like in ros1 sensor\_msgs/laserscan.h

Did you add `sensor_msgs` as a dependency when creating your package? I suppose `sensor_msgs/msg/laserscan.hpp` should work.

> [@t.alscher](#):
>
> The /kobuki/laser/scan topic doesn’t have a subscriber or publisher if I make ros2 topic info on it (the bridge is running).

Yes, it won’t have a publisher, and you need to create a subscriber for it.

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<div class="post-metadata">

**Author:** ![t.alscher](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/t.alscher/32/10_2.png) [@t.alscher](https://get-help.theconstruct.ai/u/t.alscher)\
**Post date:** [June 10, 2020, 5:56am UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/3 "2020-06-10T05:56:44Z")

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sensor\_msgs is included as a dependencie and as a required package

 ![ROS2Problem](https://get-help.robotigniteacademy.com/uploads/default/original/2X/2/231519c3d835b4a698a60e7bf8f69c70222501e4.png)

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<div class="post-metadata">

**Author:** ![bayodesegun](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/bayodesegun/32/6966_2.png) [@bayodesegun](https://get-help.theconstruct.ai/u/bayodesegun)\
**Post date:** [June 10, 2020, 9:45am UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/4 "2020-06-10T09:45:54Z")

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Sorry for the confusion. The right message name is `sensor_msgs/msg/laser_scan.hpp`.

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<div class="post-metadata">

**Author:** ![t.alscher](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/t.alscher/32/10_2.png) [@t.alscher](https://get-help.theconstruct.ai/u/t.alscher)\
**Post date:** [June 11, 2020, 6:59am UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/5 "2020-06-11T06:59:17Z")

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This worked.  
But can you tell me how I should have gotten this information, so that I know this for future projects 😅

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<div class="post-metadata">

**Author:** ![bayodesegun](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/bayodesegun/32/6966_2.png) [@bayodesegun](https://get-help.theconstruct.ai/u/bayodesegun)\
**Post date:** [June 11, 2020, 11:05am UTC](https://get-help.theconstruct.ai/t/topics-mini-project-laserscan-library-confusion/3965/6 "2020-06-11T11:05:47Z")

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Yes, I took a peek at the `/opt/ros/dashing/include/sensor_msgs/` directory to check the name of the messages.

It also appears that, by convention, a message named CamelCase would be `camel_case.hpp`, but the “final word” would be the actual message name in that directory.