ROS2与C++入门教程-创建服务（srv）文件

ROS2与C++入门教程-创建服务（srv）文件

说明：

• 介绍如何创建服务srv文件

步骤：

• 使用已经建好的工作空间dev_ws
• 新建包，如果已经建好，忽略这行

cd ~/dev-ws/src
ros2 pkg create --build-type ament_cmake tutorial_interfaces

• 新建目录mkdir srv

cd ~/dev-ws/src/tutorial_interfaces
mkdir srv

• 增加msg定义文件

cd ~/dev-ws/src/tutorial_interfaces/srv
vim AddThreeInts.srv

• 内容如下：

int64 a
int64 b
int64 c
---
int64 sum

• 定义一个a b c三个输入，输出sum，都是整数
• 编辑CMakeLists.txt，增加如下行

find_package(rosidl_default_generators REQUIRED)

rosidl_generate_interfaces(${PROJECT_NAME}
  "srv/AddThreeInts.srv"
 )

• 编辑package.xml，增加如下行

<build_depend>rosidl_default_generators</build_depend>
<exec_depend>rosidl_default_runtime</exec_depend>
<member_of_group>rosidl_interface_packages</member_of_group>

• 编译包

cd ~/dev_ws/
colcon build --symlink-install --packages-select tutorial_interfaces

• 接着重新加载工作空间

. install/setup.bash

• 查询消息接口

ros2 interface show tutorial_interfaces/srv/AddThreeInts

• 效果如下：

int64 a
int64 b
int64 c
---
int64 sum

测试：

• 使用之前的cpp_pubsub包的发布
• 修改服务端，进入srv目录，新建文件add_two_ints_server_srv.cpp

vim add_two_ints_server_srv.cpp

• 内容如下：

#include "rclcpp/rclcpp.hpp"
#include "tutorial_interfaces/srv/add_three_ints.hpp"     // CHANGE

#include <memory>

void add(const std::shared_ptr<tutorial_interfaces::srv::AddThreeInts::Request> request,     // CHANGE
          std::shared_ptr<tutorial_interfaces::srv::AddThreeInts::Response>       response)  // CHANGE
{
  response->sum = request->a + request->b + request->c;                                       // CHANGE
  RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Incoming request\na: %ld" " b: %ld" " c: %ld",   // CHANGE
                request->a, request->b, request->c);                                          // CHANGE
  RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "sending back response: [%ld]", (long int)response->sum);
}

int main(int argc, char **argv)
{
  rclcpp::init(argc, argv);

  std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("add_three_ints_server");  // CHANGE

  rclcpp::Service<tutorial_interfaces::srv::AddThreeInts>::SharedPtr service =                 // CHANGE
    node->create_service<tutorial_interfaces::srv::AddThreeInts>("add_three_ints",  &add);     // CHANGE

  RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Ready to add three ints.");      // CHANGE

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

• 修改客户端，进入srv目录，新建文件add_two_ints_client_srv.cpp
• 如下内容：

#include "rclcpp/rclcpp.hpp"
#include "tutorial_interfaces/srv/add_three_ints.hpp"        // CHANGE

#include <chrono>
#include <cstdlib>
#include <memory>

using namespace std::chrono_literals;

int main(int argc, char **argv)
{
  rclcpp::init(argc, argv);

  if (argc != 4) { // CHANGE
      RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "usage: add_three_ints_client X Y Z");      // CHANGE
      return 1;
  }

  std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("add_three_ints_client"); // CHANGE
  rclcpp::Client<tutorial_interfaces::srv::AddThreeInts>::SharedPtr client =                        // CHANGE
    node->create_client<tutorial_interfaces::srv::AddThreeInts>("add_three_ints");                  // CHANGE

  auto request = std::make_shared<tutorial_interfaces::srv::AddThreeInts::Request>();               // CHANGE
  request->a = atoll(argv[1]);
  request->b = atoll(argv[2]);
  request->c = atoll(argv[3]);               // CHANGE

  while (!client->wait_for_service(1s)) {
    if (!rclcpp::ok()) {
      RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Interrupted while waiting for the service. Exiting.");
      return 0;
    }
    RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "service not available, waiting again...");
  }

  auto result = client->async_send_request(request);
  // Wait for the result.
  if (rclcpp::spin_until_future_complete(node, result) ==
    rclcpp::executor::FutureReturnCode::SUCCESS)
  {
    RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Sum: %ld", result.get()->sum);
  } else {
    RCLCPP_ERROR(rclcpp::get_logger("rclcpp"), "Failed to call service add_three_ints");    // CHANGE
  }

  rclcpp::shutdown();
  return 0;
}

• 修改CMakelist.txt 如下

 find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(tutorial_interfaces REQUIRED)        # CHANGE

add_executable(server_srv src/add_two_ints_server_srv.cpp)
ament_target_dependencies(server_srv
  rclcpp tutorial_interfaces)                      #CHANGE

add_executable(client_srv src/add_two_ints_client_srv.cpp)
ament_target_dependencies(client_srv
  rclcpp tutorial_interfaces)                      #CHANGE

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


ament_package()

• 修改package.xml 增加依赖

<depend>tutorial_interfaces</depend>

• 编译包

colcon build --packages-select cpp_srvcli

• 新开终端，启动服务端

ros2 run cpp_srvcli server_srv

• 新开终端，启动客户端

ros2 run cpp_srvcli client_srv 2 3 1