ROS学习(五）客户端与服务端通信_client.call

目录

 服务模型

一、实现客户端

1.创建服务功能包

2.创建turtle_spawn.cpp

3.配置CMakeLists.txt

4.编译

5.运行

二、实现服务端

1.创建turtle_command_server.cpp

2.配置CMakeLists.txt

3.编译

4.运行

 三、自定义服务

1.创建srv文件

2.在 package.xml中添加功能依赖包

3.在CMakeLists.txt添加编译选项

4.编译

5.应用此自定义服务

---

服务模型

实现过程
客户端(Client)产生请求的节点，发布请求，服务端(Server)做出操作并给客户端回馈

---

ros服务端与客户端通信https://download.csdn.net/download/m0_56451176/86398723?spm=1001.2014.3001.5503 

一、实现客户端

实现目的：通过客户端请求海龟仿真器产生第二子海龟

1.创建服务功能包

cd ~/catkin_ws/src
catkin_create_pkg learning_service roscpp rospy std_msgs geometry_msgs turtlesim

2.创建turtle_spawn.cpp

cd learning_service/src
touch turtle_spawn.cpp
gedit turtle_spawn.cpp

turtle_spawn.cpp内容如下：

//该例程将请求/spawn服务，服务数据类型turtlesim::Spawn
#include <ros/ros.h>
#include <turtlesim/Spawn.h>
int main(int argc, char** argv)
{
    // 初始化ROS节点
	ros::init(argc, argv, "turtle_spawn");
 
    // 创建节点句柄
	ros::NodeHandle node;
 
    // 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
	ros::service::waitForService("/spawn");		//若找不到服务则一直等待
	ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");
 
    // 初始化turtlesim::Spawn的请求数据
	turtlesim::Spawn srv;
	srv.request.x = 2.0;
	srv.request.y = 2.0;
	srv.request.name = "turtle2";
 
    // 请求服务调用
	ROS_INFO("Call service to spwan turtle[x:%0.6f, y:%0.6f, name:%s]", srv.request.x, srv.request.y, srv.request.name.c_str());
	add_turtle.call(srv);		//发出请求，等待反馈
 
	// 显示服务调用结果
	ROS_INFO("Spwan turtle successfully [name:%s]", srv.response.name.c_str());
	return 0;
};

3.配置CMakeLists.txt

在build区域中添加：

add_executable(turtle_spawn src/turtle_spawn.cpp)		
target_link_libraries(turtle_spawn ${catkin_LIBRARIES})	

4.编译

cd ~/catkin_ws
catkin_make

5.运行

启动ROS核心 

roscore

启动海龟仿真器 

rosrun turtlesim turtlesim_node

运行客户端 

source ~/catkin_ws/devel/setup.bash
rosrun learning_service turtle_spawn

效果为产生第二只海龟

---

二、实现服务端

实现目的：控制海龟运动

1.创建turtle_command_server.cpp

cd ~/catkin_ws/src/learning_service/src
touch turtle_command_server.cpp
gedit turtle_command_server.cpp

turtle_command_server.cpp内容如下：

//该例程将执行/turtle_command服务，服务数据类型std_srvs/Trigger
#include <ros/ros.h>
#include <geometry_msgs/Twist.h>
#include <std_srvs/Trigger.h>
ros::Publisher turtle_vel_pub;
bool pubCommand = false;	//是否在运动的标志，作为开关
 
// service回调函数，输入参数req，输出参数res
bool commandCallback(std_srvs::Trigger::Request &req,std_srvs::Trigger::Response &res)
{
	pubCommand = !pubCommand;
 
    // 显示请求数据
    ROS_INFO("Publish turtle velocity command [%s]", pubCommand==true?"Yes":"No");
 
	// 设置反馈数据
	res.success = true;		//在服务中显示输出
	res.message = "Change turtle command state!";
    return true;
}
 
int main(int argc, char **argv)
{
    // ROS节点初始化
    ros::init(argc, argv, "turtle_command_server");
 
    // 创建节点句柄
    ros::NodeHandle n;
 
    // 创建一个名为/turtle_command的server，注册回调函数commandCallback
    ros::ServiceServer command_service = n.advertiseService("/turtle_command", commandCallback);
 
	// 创建一个Publisher，发布名为/turtle1/cmd_vel的topic，消息类型为geometry_msgs::Twist，队列长度10
	turtle_vel_pub = n.advertise<geometry_msgs::Twist>("/turtle1/cmd_vel", 10);
 
    // 循环等待回调函数
    ROS_INFO("Ready to receive turtle command.");
 
	// 设置循环的频率
	ros::Rate loop_rate(10);
	while(ros::ok())
    {
		// 查看一次回调函数队列
    	ros::spinOnce();
 
		// 如果标志为true，则发布速度指令
		if(pubCommand)
        {
			geometry_msgs::Twist vel_msg;
			vel_msg.linear.x = 0.5;
			vel_msg.angular.z = 0.2;
			turtle_vel_pub.publish(vel_msg);
		}
		//按照循环频率延时
	    loop_rate.sleep();
	}
    return 0;
}

2.配置CMakeLists.txt

在build区域中添加：

add_executable(turtle_command_server src/turtle_command_server.cpp)
target_link_libraries(turtle_command_server ${catkin_LIBRARIES})

3.编译

cd ~/catkin_ws
catkin_make

4.运行

启动ROS核心 

roscore

启动海龟仿真器 

rosrun turtlesim turtlesim_node

运行服务端 

source ~/catkin_ws/devel/setup.bash
rosrun learning_service turtle_command_server

运行turtle_command服务

rosservice call /turtle_command "{}"	

---

 三、自定义服务

1.创建srv文件

cd ~/catkin_ws/src/learning_service
mkdir srv
cd srv
touch Person.srv
gedit Person.srv

Person.srv内容如下

string name
uint8 age
uint8 sex
uint8 unknown = 0
uint8 male = 1
uint8 female = 2
---					
string result

注：三根横线上为request数据，下方为response 

2.在 package.xml中添加功能依赖包

在服务功能包的package.xml中添加功能包的编译依赖和运行依赖

<build_depend>message_generation</build_depend>		
<exec_depend>message_runtime</exec_depend>			

3.在CMakeLists.txt添加编译选项

find_package(...message_generation)
 
#依赖，在messages，services栏中加
add_service_files(FILES Person.srv)			
generate_messages(DEPENDENCIES std_msgs)	
 
#依赖若被注释要取消
catkin_package(...message_runtime)    

  

 

4.编译

cd ~/catkin_ws
catkin_make

此时在devel/include/功能包目录下会生成srv文件定义的整体头文件，三横线前在request头文件，三横线下在response头文件，其信息即为在srv中定义的内容，应用时引入Person.h即可

5.应用此自定义服务

1.在话题功能包的src目录下创建person_client.cpp

cd ~/catkin_ws/src/learning_service/src
touch person_client.cpp
gedit person_client.cpp

 person_client.cpp内容如下

//该例程将请求/show_person服务，服务数据类型learning_service::Person
#include <ros/ros.h>
#include "learning_service/Person.h"
int main(int argc, char** argv){
    // 初始化ROS节点
	ros::init(argc, argv, "person_client");
    // 创建节点句柄
	ros::NodeHandle node;
    // 发现/spawn服务后，创建一个服务客户端，连接名为/show_person的service
	ros::service::waitForService("/show_person");
	ros::ServiceClient person_client = node.serviceClient<learning_service::Person>("/show_person");
    // 初始化learning_service::Person的请求数据
	learning_service::Person srv;	//定义Person的对象
	srv.request.name = "Tom";
	srv.request.age  = 20;
	srv.request.sex  = learning_service::Person::Request::male;
    // 请求服务调用
	ROS_INFO("Call service to show person[name:%s, age:%d, sex:%d]", srv.request.name.c_str(), srv.request.age, srv.request.sex);
	person_client.call(srv);
	// 显示服务调用结果
	ROS_INFO("Show person result : %s", srv.response.result.c_str());
	return 0;
}

2.创建person_server.cpp

在服务功能包的src目录下创建person_server.cpp

cd ~/catkin_ws/src/learning_service/src
touch person_server.cpp
gedit person_server.cpp

person_server.cpp内容如下

//该例程将执行/show_person服务，服务数据类型learning_service::Person
#include <ros/ros.h>
#include "learning_service/Person.h"
// service回调函数，输入参数req，输出参数res
bool personCallback(learning_service::Person::Request  &req,learning_service::Person::Response &res){
    // 显示请求数据
    ROS_INFO("Person: name:%s  age:%d  sex:%d", req.name.c_str(), req.age, req.sex);
	// 设置反馈数据
	res.result = "OK";
    return true;
}
 
int main(int argc, char **argv){
    // ROS节点初始化
    ros::init(argc, argv, "person_server");
    // 创建节点句柄
    ros::NodeHandle n;
    // 创建一个名为/show_person的server，注册回调函数personCallback
    ros::ServiceServer person_service = n.advertiseService("/show_person", personCallback);
    // 循环等待回调函数
    ROS_INFO("Ready to show person informtion.");
    ros::spin();
    return 0;
}

3.配置功能包的CMakeLists.txt中的编译规则，build栏中

add_executable(person_server src/person_server.cpp)			
target_link_libraries(person_server ${catkin_LIBRARIES})	
add_dependencies(person_server ${PROJECT_NAME}_gencpp)		
 
add_executable(person_client src/person_client.cpp)
target_link_libraries(person_client ${catkin_LIBRARIES})
add_dependencies(person_client ${PROJECT_NAME}_gencpp)

 4.编译

cd ~/catkin_ws
catkin_make

5.运行

roscore

source ~/catkin_ws/devel/setup.bash
rosrun learning_service person_server

source ~/catkin_ws/devel/setup.bash
rosrun learning_service person_client

 注：spinOnce()执行后还会执行之后的程序，而spin()不会

先打开服务端，再开客户端，服务端可直接反馈
若服务端未开，则在waitForService函数等待服务端，当服务端可用即可请求并反馈