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Client（客户端）：发布海龟生成请求 [类似Publisher]
Serve（服务端）：海龟仿真器,接收请求 [类似于Subscriber]
Service（服务）：生成海龟的具体内容，其中服务类型是turtlesim::Spawn[类似于Topic]

创建功能包：

cd catkin_ws/src
catkin_create_pkg learning_service roscpp rospy std_msgs geometry_msgs turtlesim

功能包名:learning_service + 依赖

/*** 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>  //包含头文件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// 查询是否有名为spawn的服务，有则请求该服务，否则一直等待下去（阻塞型函数）ros::service::waitForService("/spawn");// 创建ServiceClient客户端，给spawn服务发送请求，<>中为请求的数据类型，()中为服务名ros::ServiceClient add_turtle = node.serviceClient<turtlesim::Spawn>("/spawn");// 初始化turtlesim::Spawn的请求数据（产生一只新的海龟）turtlesim::Spawn srv; //srvsrv.request.x = 2.0;  //x坐标srv.request.y = 2.0;  //y坐标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); //阻塞型函数// 显示服务调用结果ROS_INFO("Spwan turtle successfully [name:%s]", srv.response.name.c_strreturn 0;}