Contents
  1. I. Objective
  2. II. Create the Package
  3. III. Create the Client Code
  4. IV. Configure the Compilation Rules for the Client Code
  5. V. Build and Run

I. Objective

Send a service request programmatically.

In other words, the client sends a request to the server to spawn a turtle, and the server returns the response to the client.

II. Create the Package

Go back to the catkin_ws/src directory and create a package named learning_service.

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

II. Create the Package

III. Create the Client Code

In the ~/catkin_ws/src/learning_service/src directory, create a file named turtle_spawn.cpp with the following contents:

/**
 * 该例程将请求/spawn服务，服务数据类型turtlesim::Spawn
 REFERENC:www.guyuehome.com.
 */

#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 spawn 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("Spawn turtle successfully [name:%s]", srv.response.name.c_str());

	return 0;
};

The code 👆 is implemented in the following steps:

  1. Initialize the ROS node
  2. Create a Client instance
  3. Send the service request data
  4. Wait for the response after the Server processes the request III. Create the Client Code

IV. Configure the Compilation Rules for the Client Code

In learning_service, open CMakeLists.txt and add the following code in the area shown:

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

add_executable adds a compilation rule, and target_link_libraries links some required libraries. IV. Configure the Compilation Rules for the Client Code

V. Build and Run

Build:

cd ~/catkin_ws
catkin_make

V. Build and Run

Run the client. You can see that a second turtle has been spawned.

source devel/setup.bash
roscore
rosrun turtlesim turtlesim_node
rosrun learning_service turtle_spawn

V. Build and Run (2)