https://github.com/ivanitskiy/ros_simple_pubsub

Demo pub-sub package for Robot Operating System (ROS)
https://github.com/ivanitskiy/ros_simple_pubsub

ros ros-melodic

Last synced: 27 days ago
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Demo pub-sub package for Robot Operating System (ROS)

• Host: GitHub
• URL: https://github.com/ivanitskiy/ros_simple_pubsub
• Owner: ivanitskiy
• License: mit
• Created: 2019-12-23T03:13:36.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2019-12-23T03:22:01.000Z (about 5 years ago)
• Last Synced: 2024-10-28T02:07:26.165Z (3 months ago)
• Topics: ros, ros-melodic
• Language: CMake
• Size: 5.86 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# ROS Node example

## Creating package

We need to setup our new workspace with command-line tools `catkin_create_pkg`. Then we will create a new ROS package. 

Create a new Workspace: 

    $ mkdir -p ~/dev/catkin_ws/src

    $ cd ~/dev/catkin_ws/src

Create a new package and specify dependencies to include:

    $ catkin_create_pkg simple_pubsub  roscpp std_msgs

Build package

    catkin_make

Remember to run `catkin_make` in the *workspace* folder.

## Implement publish subscribe

We need to implement a publish subscribe logic.

### Add publisher implementation:

Create a new file `~/dev/catkin_ws/src/simple_pubsub/src/publish.cpp`

```c++

#include "ros/ros.h" 

#include "std_msgs/String.h" 

#include  

#include 

int main(int argc, char **argv) 

{ 

  ros::init(argc, argv, "simple_publish"); 

  ros::NodeHandle n; 

  ros::Publisher chatter_pub = 

     n.advertise("message", 1000); 

  ros::Rate loop_rate(10); 

  while (ros::ok()) 

  { 

    std_msgs::String msg; 

    std::stringstream ss; 

    auto tinenow = std::chrono::system_clock::now(); 

    std::time_t _time = std::chrono::system_clock::to_time_t(tinenow);

    ss<< " I am the publish node. Current time: " << std::ctime(&_time); 

    msg.data = ss.str(); 

    //ROS_INFO("%s", msg.data.c_str()); 

    chatter_pub.publish(msg); 

    ros::spinOnce(); 

    loop_rate.sleep(); 

  } 

  return 0; 

} 

```

### Add subscriber implementation:

Create a new file `~/dev/catkin_ws/src/simple_pubsub/src/subscribe.cpp`

```c++

#include "ros/ros.h" 

#include "std_msgs/String.h" 

 

void chatterCallback(const std_msgs::String::ConstPtr msg) 

{ 

  ROS_INFO("I heard: [%s]", msg->data.c_str()); 

} 

 

int main(int argc, char **argv) 

{ 

  ros::init(argc, argv, "simple_subscribe"); 

  ros::NodeHandle n; 

  ros::Subscriber sub = n.subscribe("message", 1000, 

     chatterCallback); 

  ros::spin(); 

  return 0; 

} 

```

Update 

```cmake

cmake_minimum_required(VERSION 2.8.3)

project(simple_pubsub)

find_package(catkin REQUIRED COMPONENTS

  roscpp

  std_msgs

)

catkin_package()

include_directories(

    include ${catkin_INCLUDE_DIRS}

)

add_executable(

    ${PROJECT_NAME}_publish src/publish.cpp

)

add_executable(

    ${PROJECT_NAME}_subscribe src/subscribe.cpp

)

add_dependencies(

    ${PROJECT_NAME}_publish ${PROJECT_NAME}_generate_messages_cpp

)

add_dependencies(

    ${PROJECT_NAME}_subscribe ${PROJECT_NAME}_generate_messages_cpp

)

target_link_libraries(

    ${PROJECT_NAME}_publish ${catkin_LIBRARIES}

)

target_link_libraries(

    ${PROJECT_NAME}_subscribe ${catkin_LIBRARIES}

)

```

## 

Start a master node in a new terminal:

    

    roscore

Start publisher in a new terminal:

    rosrun simple_pubsub simple_pubsub_publish

Start subscriber in a new terminal:

    rosrun simple_pubsub simple_pubsub_publish

You should see messages that publisher sends.