编写动作服务器和客户端 (c ++) [待校准@6753]

Goal目标: Goal在C++ 中实现动作服务器和客户端。 [待校准@6754]

Tutorial教程级别: Intermediate中级 [待校准@6713]

内容

背景
先决条件
任务
总结
相关内容

背景 

[需手动修复的语法]Action是ROS中的一种异步通讯形式。* [需手动修复的语法]Action客户端 * 向 * 动作服务器 * 发送目标请求。* [需手动修复的语法]Action服务器 * 向 * 动作客户端 * 发送目标反馈和结果。 [待校准@6756]

先决条件 

您将需要上一教程 “ 创建动作 [待校准@6711] ” 中定义的 action_tutorials_interfaces 包和 Fibonacci.action 接口。 [待校准@6757]

任务 

1创建action_tutorials_cpp包 [机器人@6758]

正如我们在创建您的第一个ROS 2包 [待校准@7117] 教程中看到的，我们需要创建一个新的包来保存我们的C++ 和支持性代码。 [待校准@6759]

1.1创建动作 _ 教程 _ cpp包 [待校准@6760]

进入您在 previous tutorial 中创建的动作工作区 (请记住为工作区源文件)，并为c动作服务器创建一个新包: [待校准@6761]

cd ~/action_ws/src
ros2 pkg create --dependencies action_tutorials_interfaces rclcpp rclcpp_action rclcpp_components -- action_tutorials_cpp

cd ~/action_ws/src
ros2 pkg create --dependencies action_tutorials_interfaces rclcpp rclcpp_action rclcpp_components -- action_tutorials_cpp

cd \dev\action_ws\src
ros2 pkg create --dependencies action_tutorials_interfaces rclcpp rclcpp_action rclcpp_components -- action_tutorials_cpp

1.2添加可见性控制 [待校准@6762]

为了使包编译并在Windows上工作，我们需要添加一些 "visibility control" 。有关为什么需要这样做的详细信息，请参阅 here 。 [待校准@6763]

打开 action_tutorials_cpp/include/action_tutorials_cpp/visibility_control.h ，放入以下代码: [待校准@6764]

#ifndef ACTION_TUTORIALS_CPP__VISIBILITY_CONTROL_H_
#define ACTION_TUTORIALS_CPP__VISIBILITY_CONTROL_H_

#ifdef __cplusplus
extern "C"
{
#endif

// This logic was borrowed (then namespaced) from the examples on the gcc wiki:
//     https://gcc.gnu.org/wiki/Visibility

#if defined _WIN32 || defined __CYGWIN__
  #ifdef __GNUC__
    #define ACTION_TUTORIALS_CPP_EXPORT __attribute__ ((dllexport))
    #define ACTION_TUTORIALS_CPP_IMPORT __attribute__ ((dllimport))
  #else
    #define ACTION_TUTORIALS_CPP_EXPORT __declspec(dllexport)
    #define ACTION_TUTORIALS_CPP_IMPORT __declspec(dllimport)
  #endif
  #ifdef ACTION_TUTORIALS_CPP_BUILDING_DLL
    #define ACTION_TUTORIALS_CPP_PUBLIC ACTION_TUTORIALS_CPP_EXPORT
  #else
    #define ACTION_TUTORIALS_CPP_PUBLIC ACTION_TUTORIALS_CPP_IMPORT
  #endif
  #define ACTION_TUTORIALS_CPP_PUBLIC_TYPE ACTION_TUTORIALS_CPP_PUBLIC
  #define ACTION_TUTORIALS_CPP_LOCAL
#else
  #define ACTION_TUTORIALS_CPP_EXPORT __attribute__ ((visibility("default")))
  #define ACTION_TUTORIALS_CPP_IMPORT
  #if __GNUC__ >= 4
    #define ACTION_TUTORIALS_CPP_PUBLIC __attribute__ ((visibility("default")))
    #define ACTION_TUTORIALS_CPP_LOCAL  __attribute__ ((visibility("hidden")))
  #else
    #define ACTION_TUTORIALS_CPP_PUBLIC
    #define ACTION_TUTORIALS_CPP_LOCAL
  #endif
  #define ACTION_TUTORIALS_CPP_PUBLIC_TYPE
#endif

#ifdef __cplusplus
}
#endif

#endif  // ACTION_TUTORIALS_CPP__VISIBILITY_CONTROL_H_

2编写动作服务器 [待校准@6765]

让我们集中精力编写一个动作服务器，使用我们在创建动作 [待校准@6711] 教程中创建的动作来计算斐波那契序列。 [待校准@6766]

2.1编写动作服务器代码 [待校准@6767]

打开 action_tutorials_cpp/src/fibonacci_action_server.cpp ，放入以下代码: [待校准@6768]

#include <functional>
#include <memory>
#include <thread>

#include "action_tutorials_interfaces/action/fibonacci.hpp"
#include "rclcpp/rclcpp.hpp"
#include "rclcpp_action/rclcpp_action.hpp"
#include "rclcpp_components/register_node_macro.hpp"

#include "action_tutorials_cpp/visibility_control.h"

namespace action_tutorials_cpp
{
class FibonacciActionServer : public rclcpp::Node
{
public:
  using Fibonacci = action_tutorials_interfaces::action::Fibonacci;
  using GoalHandleFibonacci = rclcpp_action::ServerGoalHandle<Fibonacci>;

  ACTION_TUTORIALS_CPP_PUBLIC
  explicit FibonacciActionServer(const rclcpp::NodeOptions & options = rclcpp::NodeOptions())
  : Node("fibonacci_action_server", options)
  {
    using namespace std::placeholders;

    this->action_server_ = rclcpp_action::create_server<Fibonacci>(
      this,
      "fibonacci",
      std::bind(&FibonacciActionServer::handle_goal, this, _1, _2),
      std::bind(&FibonacciActionServer::handle_cancel, this, _1),
      std::bind(&FibonacciActionServer::handle_accepted, this, _1));
  }

private:
  rclcpp_action::Server<Fibonacci>::SharedPtr action_server_;

  rclcpp_action::GoalResponse handle_goal(
    const rclcpp_action::GoalUUID & uuid,
    std::shared_ptr<const Fibonacci::Goal> goal)
  {
    RCLCPP_INFO(this->get_logger(), "Received goal request with order %d", goal->order);
    (void)uuid;
    return rclcpp_action::GoalResponse::ACCEPT_AND_EXECUTE;
  }

  rclcpp_action::CancelResponse handle_cancel(
    const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    RCLCPP_INFO(this->get_logger(), "Received request to cancel goal");
    (void)goal_handle;
    return rclcpp_action::CancelResponse::ACCEPT;
  }

  void handle_accepted(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    using namespace std::placeholders;
    // this needs to return quickly to avoid blocking the executor, so spin up a new thread
    std::thread{std::bind(&FibonacciActionServer::execute, this, _1), goal_handle}.detach();
  }

  void execute(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    RCLCPP_INFO(this->get_logger(), "Executing goal");
    rclcpp::Rate loop_rate(1);
    const auto goal = goal_handle->get_goal();
    auto feedback = std::make_shared<Fibonacci::Feedback>();
    auto & sequence = feedback->partial_sequence;
    sequence.push_back(0);
    sequence.push_back(1);
    auto result = std::make_shared<Fibonacci::Result>();

    for (int i = 1; (i < goal->order) && rclcpp::ok(); ++i) {
      // Check if there is a cancel request
      if (goal_handle->is_canceling()) {
        result->sequence = sequence;
        goal_handle->canceled(result);
        RCLCPP_INFO(this->get_logger(), "Goal canceled");
        return;
      }
      // Update sequence
      sequence.push_back(sequence[i] + sequence[i - 1]);
      // Publish feedback
      goal_handle->publish_feedback(feedback);
      RCLCPP_INFO(this->get_logger(), "Publish feedback");

      loop_rate.sleep();
    }

    // Check if goal is done
    if (rclcpp::ok()) {
      result->sequence = sequence;
      goal_handle->succeed(result);
      RCLCPP_INFO(this->get_logger(), "Goal succeeded");
    }
  }
};  // class FibonacciActionServer

}  // namespace action_tutorials_cpp

RCLCPP_COMPONENTS_REGISTER_NODE(action_tutorials_cpp::FibonacciActionServer)

前几行包括我们需要编译的所有标头。 [待校准@6769]

接下来，我们创建一个类，该类是 “rclcpp:: node” 的派生类: [待校准@6770]

class FibonacciActionServer : public rclcpp::Node

[需手动修复的语法] FibonacciActionServer 类的构造函数将节点名称初始化为 fibonacci_action_server : [待校准@6771]

  explicit FibonacciActionServer(const rclcpp::NodeOptions & options = rclcpp::NodeOptions())
  : Node("fibonacci_action_server", options)

构造函数还实例化新的动作服务器: [待校准@6772]

    this->action_server_ = rclcpp_action::create_server<Fibonacci>(
      this,
      "fibonacci",
      std::bind(&FibonacciActionServer::handle_goal, this, _1, _2),
      std::bind(&FibonacciActionServer::handle_cancel, this, _1),
      std::bind(&FibonacciActionServer::handle_accepted, this, _1));

一个动作服务器需要6件事: [待校准@6773]

模板化动作类型名称: Fibonacci 。 [待校准@6774]
一个ROS 2节点，用于将动作添加到: this 。 [待校准@6775]
动作名称: “'fibonacci'”。 [待校准@6776]
用于处理目标的调用返回函数: handle_goal [待校准@6777]
用于处理取消的调用返回函数: handle_cancel 。 [待校准@6778]
用于处理目标接受的调用返回函数: handle_accept 。 [待校准@6779]

接下来是文件中各种调用的实现。请注意，所有的调用都需要快速返回，否则我们有可能使执行程序挨饿。 [待校准@6780]

我们首先调用back来处理新目标: [待校准@6781]

  rclcpp_action::GoalResponse handle_goal(
    const rclcpp_action::GoalUUID & uuid,
    std::shared_ptr<const Fibonacci::Goal> goal)
  {
    RCLCPP_INFO(this->get_logger(), "Received goal request with order %d", goal->order);
    (void)uuid;
    return rclcpp_action::GoalResponse::ACCEPT_AND_EXECUTE;
  }

此实现仅接受所有目标。 [待校准@6782]

接下来是处理取消的调用: [待校准@6783]

  rclcpp_action::CancelResponse handle_cancel(
    const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    RCLCPP_INFO(this->get_logger(), "Received request to cancel goal");
    (void)goal_handle;
    return rclcpp_action::CancelResponse::ACCEPT;
  }

这个实现只是告诉客户端它接受了取消。 [待校准@6784]

最后一个调用back接受一个新目标并开始处理它: [待校准@6785]

  void handle_accepted(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    using namespace std::placeholders;
    // this needs to return quickly to avoid blocking the executor, so spin up a new thread
    std::thread{std::bind(&FibonacciActionServer::execute, this, _1), goal_handle}.detach();
  }

由于执行是一个长期运行的操作，我们生成一个线程来完成实际工作，并快速从 handle_accepted 返回。 [待校准@6786]

所有进一步的处理和更新都在新线程的 execute 方法中完成: [待校准@6787]

  void execute(const std::shared_ptr<GoalHandleFibonacci> goal_handle)
  {
    RCLCPP_INFO(this->get_logger(), "Executing goal");
    rclcpp::Rate loop_rate(1);
    const auto goal = goal_handle->get_goal();
    auto feedback = std::make_shared<Fibonacci::Feedback>();
    auto & sequence = feedback->partial_sequence;
    sequence.push_back(0);
    sequence.push_back(1);
    auto result = std::make_shared<Fibonacci::Result>();

    for (int i = 1; (i < goal->order) && rclcpp::ok(); ++i) {
      // Check if there is a cancel request
      if (goal_handle->is_canceling()) {
        result->sequence = sequence;
        goal_handle->canceled(result);
        RCLCPP_INFO(this->get_logger(), "Goal canceled");
        return;
      }
      // Update sequence
      sequence.push_back(sequence[i] + sequence[i - 1]);
      // Publish feedback
      goal_handle->publish_feedback(feedback);
      RCLCPP_INFO(this->get_logger(), "Publish feedback");

      loop_rate.sleep();
    }

    // Check if goal is done
    if (rclcpp::ok()) {
      result->sequence = sequence;
      goal_handle->succeed(result);
      RCLCPP_INFO(this->get_logger(), "Goal succeeded");
    }
  }

这个工作线程每秒处理一个斐波那契序列的序列号，发布每个步骤的反馈更新。加工完成后，它将 goal_handle 标记为成功，然后退出。 [待校准@6788]

我们现在有了一个功能齐全的动作服务器。让我们构建并运行它。 [待校准@6789]

2.2编译动作服务器 [待校准@6790]

在上一节中，我们将动作服务器代码放在适当的位置。为了让它编译并运行，我们需要做一些额外的事情。 [待校准@6791]

首先，我们需要设置CMakeLists.txt，以便编译动作服务器。打开 action_tutorials_cpp/CMakeLists.txt ，在 find_package 调用后添加以下内容: [待校准@6792]

add_library(action_server SHARED
  src/fibonacci_action_server.cpp)
target_include_directories(action_server PRIVATE
  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
  $<INSTALL_INTERFACE:include>)
target_compile_definitions(action_server
  PRIVATE "ACTION_TUTORIALS_CPP_BUILDING_DLL")
ament_target_dependencies(action_server
  "action_tutorials_interfaces"
  "rclcpp"
  "rclcpp_action"
  "rclcpp_components")
rclcpp_components_register_node(action_server PLUGIN "action_tutorials_cpp::FibonacciActionServer" EXECUTABLE fibonacci_action_server)
install(TARGETS
  action_server
  ARCHIVE DESTINATION lib
  LIBRARY DESTINATION lib
  RUNTIME DESTINATION bin)

现在我们可以编译这个包了。转到 action_ws 的顶层，然后运行: [待校准@6793]

colcon build

这应该编译整个工作区，包括 fibonacci_action_server 在 action_tutorials_cpp 包。 [待校准@6794]

2.3运行动作服务器 [待校准@6795]

现在我们已经构建了动作服务器，我们可以运行它了。获取我们刚刚构建的工作区 ( action_ws )，并尝试运行动作服务器: [待校准@6796]

ros2 run action_tutorials_cpp fibonacci_action_server

3编写动作客户端 [待校准@6797]

3.1编写动作客户端代码 [待校准@6798]

打开 action_tutorials_cpp/src/fibonacci_action_client.cpp ，放入以下代码: [待校准@6799]

#include <functional>
#include <future>
#include <memory>
#include <string>
#include <sstream>

#include "action_tutorials_interfaces/action/fibonacci.hpp"

#include "rclcpp/rclcpp.hpp"
#include "rclcpp_action/rclcpp_action.hpp"
#include "rclcpp_components/register_node_macro.hpp"

namespace action_tutorials_cpp
{
class FibonacciActionClient : public rclcpp::Node
{
public:
  using Fibonacci = action_tutorials_interfaces::action::Fibonacci;
  using GoalHandleFibonacci = rclcpp_action::ClientGoalHandle<Fibonacci>;

  explicit FibonacciActionClient(const rclcpp::NodeOptions & options)
  : Node("fibonacci_action_client", options)
  {
    this->client_ptr_ = rclcpp_action::create_client<Fibonacci>(
      this,
      "fibonacci");

    this->timer_ = this->create_wall_timer(
      std::chrono::milliseconds(500),
      std::bind(&FibonacciActionClient::send_goal, this));
  }

  void send_goal()
  {
    using namespace std::placeholders;

    this->timer_->cancel();

    if (!this->client_ptr_->wait_for_action_server()) {
      RCLCPP_ERROR(this->get_logger(), "Action server not available after waiting");
      rclcpp::shutdown();
    }

    auto goal_msg = Fibonacci::Goal();
    goal_msg.order = 10;

    RCLCPP_INFO(this->get_logger(), "Sending goal");

    auto send_goal_options = rclcpp_action::Client<Fibonacci>::SendGoalOptions();
    send_goal_options.goal_response_callback =
      std::bind(&FibonacciActionClient::goal_response_callback, this, _1);
    send_goal_options.feedback_callback =
      std::bind(&FibonacciActionClient::feedback_callback, this, _1, _2);
    send_goal_options.result_callback =
      std::bind(&FibonacciActionClient::result_callback, this, _1);
    this->client_ptr_->async_send_goal(goal_msg, send_goal_options);
  }

private:
  rclcpp_action::Client<Fibonacci>::SharedPtr client_ptr_;
  rclcpp::TimerBase::SharedPtr timer_;

  void goal_response_callback(std::shared_future<GoalHandleFibonacci::SharedPtr> future)
  {
    auto goal_handle = future.get();
    if (!goal_handle) {
      RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");
    } else {
      RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");
    }
  }

  void feedback_callback(
    GoalHandleFibonacci::SharedPtr,
    const std::shared_ptr<const Fibonacci::Feedback> feedback)
  {
    std::stringstream ss;
    ss << "Next number in sequence received: ";
    for (auto number : feedback->partial_sequence) {
      ss << number << " ";
    }
    RCLCPP_INFO(this->get_logger(), ss.str().c_str());
  }

  void result_callback(const GoalHandleFibonacci::WrappedResult & result)
  {
    switch (result.code) {
      case rclcpp_action::ResultCode::SUCCEEDED:
        break;
      case rclcpp_action::ResultCode::ABORTED:
        RCLCPP_ERROR(this->get_logger(), "Goal was aborted");
        return;
      case rclcpp_action::ResultCode::CANCELED:
        RCLCPP_ERROR(this->get_logger(), "Goal was canceled");
        return;
      default:
        RCLCPP_ERROR(this->get_logger(), "Unknown result code");
        return;
    }
    std::stringstream ss;
    ss << "Result received: ";
    for (auto number : result.result->sequence) {
      ss << number << " ";
    }
    RCLCPP_INFO(this->get_logger(), ss.str().c_str());
    rclcpp::shutdown();
  }
};  // class FibonacciActionClient

}  // namespace action_tutorials_cpp

RCLCPP_COMPONENTS_REGISTER_NODE(action_tutorials_cpp::FibonacciActionClient)

前几行包括我们需要编译的所有标头。 [待校准@6769]

接下来，我们创建一个类，该类是 “rclcpp:: node” 的派生类: [待校准@6770]

class FibonacciActionClient : public rclcpp::Node

[需手动修复的语法] FibonacciActionClient 类的构造函数将节点名称初始化为 fibonacci_action_client : [待校准@6800]

  explicit FibonacciActionClient(const rclcpp::NodeOptions & options)
  : Node("fibonacci_action_client", options)

构造函数还实例化新的动作客户端: [待校准@6801]

    this->client_ptr_ = rclcpp_action::create_client<Fibonacci>(
      this,
      "fibonacci");

一个动作客户端需要三件事: [待校准@6802]

模板化动作类型名称: Fibonacci 。 [待校准@6774]
一个ROS 2节点，用于将动作客户端添加到: this 。 [待校准@6803]
动作名称: “'fibonacci'”。 [待校准@6776]

我们还实例化了一个ROS计时器，该计时器将启动唯一调用 send_goal : [待校准@6804]

    this->timer_ = this->create_wall_timer(
      std::chrono::milliseconds(500),
      std::bind(&FibonacciActionClient::send_goal, this));

当计时器到期时，它将调用 send_goal : [待校准@6805]

  void send_goal()
  {
    using namespace std::placeholders;

    this->timer_->cancel();

    if (!this->client_ptr_->wait_for_action_server()) {
      RCLCPP_ERROR(this->get_logger(), "Action server not available after waiting");
      rclcpp::shutdown();
    }

    auto goal_msg = Fibonacci::Goal();
    goal_msg.order = 10;

    RCLCPP_INFO(this->get_logger(), "Sending goal");

    auto send_goal_options = rclcpp_action::Client<Fibonacci>::SendGoalOptions();
    send_goal_options.goal_response_callback =
      std::bind(&FibonacciActionClient::goal_response_callback, this, _1);
    send_goal_options.feedback_callback =
      std::bind(&FibonacciActionClient::feedback_callback, this, _1, _2);
    send_goal_options.result_callback =
      std::bind(&FibonacciActionClient::result_callback, this, _1);
    this->client_ptr_->async_send_goal(goal_msg, send_goal_options);
  }

此函数执行以下操作: [待校准@6806]

取消计时器 (因此只调用一次)。 [待校准@6807]
等待动作服务器启动。 [待校准@6808]
实例化一个新的 “斐波那契:: 目标”。 [待校准@6809]
设置响应、反馈和结果调用。 [待校准@6810]
将目标发送到服务器。 [待校准@6811]

当服务器接收并接受目标时，它将向客户端发送响应。该回应由 goal_response_callback 处理: [待校准@6812]

  void goal_response_callback(std::shared_future<GoalHandleFibonacci::SharedPtr> future)
  {
    auto goal_handle = future.get();
    if (!goal_handle) {
      RCLCPP_ERROR(this->get_logger(), "Goal was rejected by server");
    } else {
      RCLCPP_INFO(this->get_logger(), "Goal accepted by server, waiting for result");
    }
  }

假设目标已被服务器接受，它将开始处理。给客户的任何反馈将由 feedback_callback 处理: [待校准@6813]

  void feedback_callback(
    GoalHandleFibonacci::SharedPtr,
    const std::shared_ptr<const Fibonacci::Feedback> feedback)
  {
    std::stringstream ss;
    ss << "Next number in sequence received: ";
    for (auto number : feedback->partial_sequence) {
      ss << number << " ";
    }
    RCLCPP_INFO(this->get_logger(), ss.str().c_str());
  }

当服务器完成处理后，它将向客户端返回结果。结果由 result_callback 处理: [待校准@6814]

  void result_callback(const GoalHandleFibonacci::WrappedResult & result)
  {
    switch (result.code) {
      case rclcpp_action::ResultCode::SUCCEEDED:
        break;
      case rclcpp_action::ResultCode::ABORTED:
        RCLCPP_ERROR(this->get_logger(), "Goal was aborted");
        return;
      case rclcpp_action::ResultCode::CANCELED:
        RCLCPP_ERROR(this->get_logger(), "Goal was canceled");
        return;
      default:
        RCLCPP_ERROR(this->get_logger(), "Unknown result code");
        return;
    }
    std::stringstream ss;
    ss << "Result received: ";
    for (auto number : result.result->sequence) {
      ss << number << " ";
    }
    RCLCPP_INFO(this->get_logger(), ss.str().c_str());
    rclcpp::shutdown();
  }

我们现在有了一个功能齐全的动作客户端。让我们构建并运行它。 [待校准@6815]

3.2编译动作客户端 [待校准@6816]

在上一节中，我们将动作客户端代码放置到位。为了让它编译并运行，我们需要做一些额外的事情。 [待校准@6817]

首先，我们需要设置CMakeLists.txt，以便编译动作客户端。打开 action_tutorials_cpp/CMakeLists.txt ，在 find_package 调用后添加以下内容: [待校准@6818]

add_library(action_client SHARED
  src/fibonacci_action_client.cpp)
target_include_directories(action_client PRIVATE
  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
  $<INSTALL_INTERFACE:include>)
target_compile_definitions(action_client
  PRIVATE "ACTION_TUTORIALS_CPP_BUILDING_DLL")
ament_target_dependencies(action_client
  "action_tutorials_interfaces"
  "rclcpp"
  "rclcpp_action"
  "rclcpp_components")
rclcpp_components_register_node(action_client PLUGIN "action_tutorials_cpp::FibonacciActionClient" EXECUTABLE fibonacci_action_client)
install(TARGETS
  action_client
  ARCHIVE DESTINATION lib
  LIBRARY DESTINATION lib
  RUNTIME DESTINATION bin)

现在我们可以编译这个包了。转到 action_ws 的顶层，然后运行: [待校准@6793]

colcon build

这应该编译整个工作区，包括 fibonacci_action_client 在 action_tutorials_cpp 包。 [待校准@6819]

3.3运行动作客户端 [待校准@6820]

现在我们已经构建了动作客户端，我们可以运行它了。首先，确保动作服务器在单独的终端中运行。现在源文件我们刚刚构建的工作区 ( action_ws )，并尝试运行动作客户端: [待校准@6821]

ros2 run action_tutorials_cpp fibonacci_action_client

您应该会看到已记录的目标被接受的消息、正在打印的反馈以及最终结果。 [待校准@6822]

总结 

在本教程中，您将c动作服务器和动作客户端逐行组合在一起，并将它们配置为交换目标、反馈和结果。 [待校准@6823]