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ROS2与C++入门教程-编写服务端和客户端 - 创客智造


ROS2与C++入门教程-编写服务端和客户端 - 创客智造_开发语言


说明:

  • 介绍如何编写服务端和客户端

编写服务端步骤:

  • 新建包cpp_srvcli

cd ~/dev_ws/src
ros2 pkg create --build-type ament_cmake cpp_srvcli --dependencies rclcpp example_interfaces

  • 依赖example_interfaces包,将会使用到example_interfaces的srv文件
  • 进入srv目录,新建文件add_two_ints_server.cpp

vim add_two_ints_server.cpp

  • 内容如下:

#include "rclcpp/rclcpp.hpp"
#include "example_interfaces/srv/add_two_ints.hpp"

#include <memory>

void add(const std::shared_ptr<example_interfaces::srv::AddTwoInts::Request> request,
std::shared_ptr<example_interfaces::srv::AddTwoInts::Response> response)
{
response->sum = request->a + request->b;
RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Incoming request\na: %ld" " b: %ld",
request->a, request->b);
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_two_ints_server");

rclcpp::Service<example_interfaces::srv::AddTwoInts>::SharedPtr service =
node->create_service<example_interfaces::srv::AddTwoInts>("add_two_ints", &add);

RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "Ready to add two ints.");

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

  • 修改CMakeLists.txt,增加如下行:

add_executable(server src/add_two_ints_server.cpp)
ament_target_dependencies(server
rclcpp example_interfaces)

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

编写客户端步骤:

  • 进入srv目录,新建文件add_two_ints_client.cpp
  • 如下内容:

#include "rclcpp/rclcpp.hpp"
#include "example_interfaces/srv/add_two_ints.hpp"

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

using namespace std::chrono_literals;

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

if (argc != 3) {
RCLCPP_INFO(rclcpp::get_logger("rclcpp"), "usage: add_two_ints_client X Y");
return 1;
}

std::shared_ptr<rclcpp::Node> node = rclcpp::Node::make_shared("add_two_ints_client");
rclcpp::Client<example_interfaces::srv::AddTwoInts>::SharedPtr client =
node->create_client<example_interfaces::srv::AddTwoInts>("add_two_ints");

auto request = std::make_shared<example_interfaces::srv::AddTwoInts::Request>();
request->a = atoll(argv[1]);
request->b = atoll(argv[2]);

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::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_two_ints");
}

rclcpp::shutdown();
return 0;
}

  • 编辑CMakeLists.txt,内容如下:

cmake_minimum_required(VERSION 3.5)
project(cpp_srvcli)

find_package(ament_cmake REQUIRED)
find_package(rclcpp REQUIRED)
find_package(example_interfaces REQUIRED)

add_executable(server src/add_two_ints_server.cpp)
ament_target_dependencies(server
rclcpp example_interfaces)

add_executable(client src/add_two_ints_client.cpp)
ament_target_dependencies(client
rclcpp example_interfaces)

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

ament_package()

编译包:

  • 安装依赖包

rosdep install -i --from-path src --rosdistro <distro> -y

  • 编译

colcon build --packages-select cpp_srvcli

测试:

  • 新开终端,启动服务端

cd ~/dev_ws/
. install/setup.bash
ros2 run cpp_srvcli server

  • 效果如下:

[INFO] [rclcpp]: Ready to add two ints.
[INFO] [rclcpp]: Incoming request
a: 2 b: 3
[INFO] [rclcpp]: sending back response: [5]

  • 新开终端,启动客户端

cd ~/dev_ws/
. install/setup.bash
ros2 run cpp_srvcli client 2 3

  • 效果如下:

[INFO] [rclcpp]: Sum: 5


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