간단하게 메시지를 발행/수신하는 예제 코드는 다음과 같습니다.

snowdeer_publisher

package.xml

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format2.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="2">
  <name>snow_publisher</name>
  <version>0.4.0</version>
  <description>Snow ROS Message Publisher</description>
  <maintainer email="snowdeer0314@gmail.com">snowdeer</maintainer>
  <license>Apache License 2.0</license>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <build_depend>rclcpp</build_depend>
  <build_depend>std_msgs</build_depend>

  <exec_depend>rclcpp</exec_depend>
  <exec_depend>std_msgs</exec_depend>
  
  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)
project(snow_publisher)

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

add_executable(${PROJECT_NAME} main.cpp)
ament_target_dependencies(${PROJECT_NAME} rclcpp std_msgs)

install(TARGETS ${PROJECT_NAME}
  DESTINATION lib/${PROJECT_NAME})

ament_package()

main.cpp

#include <cstdio>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std;
using namespace std::chrono_literals;

int main(int argc, char * argv[]) {
  
  printf("This is SnowDeer's ROS Message Publisher.\n");

  rclcpp::init(argc, argv);
  auto node = rclcpp::Node::make_shared("snowdeer_msg_publisher");
  auto publisher = node->create_publisher<std_msgs::msg::String>("snowdeer_topic");
  auto message = std::make_shared<std_msgs::msg::String>();
  auto publish_count = 0;

  rclcpp::WallRate loop_rate(1000ms);

  while (rclcpp::ok()) {
    message->data = "Hello, SnowDeer! " + std::to_string(publish_count++);

    RCLCPP_INFO(node->get_logger(), "Publishing: '%s'", message->data.c_str())
    publisher->publish(message);
    
    rclcpp::spin_some(node);

    loop_rate.sleep();
  }

  rclcpp::shutdown();
  
  return 0;
}

snowdeer_subscriber

package.xml

<?xml version="1.0"?>
<?xml-model href="http://download.ros.org/schema/package_format2.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
<package format="2">
  <name>snow_subscriber</name>
  <version>0.4.0</version>
  <description>Snow ROS Message Subscriber</description>
  <maintainer email="snowdeer0314@gmail.com">snowdeer</maintainer>
  <license>Apache License 2.0</license>

  <buildtool_depend>ament_cmake</buildtool_depend>

  <build_depend>rclcpp</build_depend>
  <build_depend>std_msgs</build_depend>

  <exec_depend>rclcpp</exec_depend>
  <exec_depend>std_msgs</exec_depend>
  
  <export>
    <build_type>ament_cmake</build_type>
  </export>
</package>

CMakeLists.txt

cmake_minimum_required(VERSION 3.5)
project(snow_subscriber)

# Default to C++14
if(NOT CMAKE_CXX_STANDARD)
  set(CMAKE_CXX_STANDARD 14)
endif()

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(std_msgs REQUIRED)

add_executable(${PROJECT_NAME} main.cpp)
ament_target_dependencies(${PROJECT_NAME} rclcpp std_msgs)

install(TARGETS ${PROJECT_NAME}
  DESTINATION lib/${PROJECT_NAME})

ament_package()

main.cpp

#include <cstdio>

#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"

using namespace std;

rclcpp::Node::SharedPtr node = nullptr;

void callback_from_topic(const std_msgs::msg::String::SharedPtr msg) {
  RCLCPP_INFO(node->get_logger(), "Received Message: '%s'", msg->data.c_str())
}

int main(int argc, char * argv[]) {
  
  printf("This is SnowDeer's ROS Message Subscriber.\n");

  rclcpp::init(argc, argv);
  node = rclcpp::Node::make_shared("snowdeer_msg_subscriber");

  auto subscription = node->create_subscription<std_msgs::msg::String>
      ("snowdeer_topic", callback_from_topic);

  rclcpp::spin(node);
  rclcpp::shutdown();

  node = nullptr;

  return 0;
}