Client客户端向Server发送请求在海龟仿真器下创建一个新的海龟

1.创建功能包

cd /catkin_ws/src
catkin_create_pkg learning_topic roscpp rospy std_msgs geometry_msgs turtlesim

  然后在你创建的learning_topic文件下的src文件下创建一个turtle_spawn.cpp文件  

touch turtle_spawn.cpp

2.创建C++文件

  在.cpp文件下输入  

/**
 * 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");
	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);

	// 显示服务调用结果
	ROS_INFO("Spwan turtle successfully [name:%s]", srv.response.name.c_str());

	return 0;
};

如何实现一个客户端

• 初始化ROS结点
• 创建一个Client实例；
• 发布服务请求数据；
• 等待Server处理之后的应答结果

3.编辑CMakeLists.txt

  加上这两句  

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

4.编译并运行

cd /catkin_ws
catkin_make

5.验证

roscore
rosrun turtlesim turtlesim_node
rosrun learning_service turtle_spawn

  当然，以上三个命令都是在不同终端下输入  

结果

  创建出一个新的小乌龟