ROS學習（十三）—— 編寫簡單的Service和Client (C++)

一、編寫Service節點

1、節點功能：

　　我們將創建一個簡單的service節點("add_two_ints_server")，該節點將接收到兩個整形數字，並返回它們的和。

 

2、beginner_tutorials包中創建src/add_two_ints_server.cpp文件  且編寫代碼

cd ~/catkin_ws/src/beginner_tutorials

 

#include "ros/ros.h"
#include "beginner_tutorials/AddTwoInts.h"   //  beginner_tutorials/AddTwoInts.h是由編譯系統自動根據我們先前創建的srv文件生成的對應該srv文件的頭文件。 

/* 這個函數提供兩個int值求和的服務，int值從request里面獲取，而返回數據裝入response內，這些數據類型都定義在srv文件內部，函數返回一個boolean值。 */
bool add(beginner_tutorials::AddTwoInts::Request  &req,
         beginner_tutorials::AddTwoInts::Response &res)
{
  res.sum = req.a + req.b;
  ROS_INFO("request: x=%ld, y=%ld", (long int)req.a, (long int)req.b);
  ROS_INFO("sending back response: [%ld]", (long int)res.sum);
  return true;
}

int main(int argc, char **argv)
{
  ros::init(argc, argv, "add_two_ints_server");
  ros::NodeHandle n;

  ros::ServiceServer service = n.advertiseService("add_two_ints", add);
  ROS_INFO("Ready to add two ints.");
  ros::spin();

  return 0;
}

 

 

二、編寫Client節點

1、在beginner_tutorials包中創建src/add_two_ints_client.cpp文件  ，幷編寫代碼

#include "ros/ros.h"
#include "beginner_tutorials/AddTwoInts.h"
#include <cstdlib>

int main(int argc, char **argv)
{
  ros::init(argc, argv, "add_two_ints_client");
  
  if (argc != 3)
  {
    ROS_INFO("usage: add_two_ints_client X Y");
    return 1;
  }

  ros::NodeHandle n;
  ros::ServiceClient client = n.serviceClient<beginner_tutorials::AddTwoInts>("add_two_ints");

  beginner_tutorials::AddTwoInts srv;
  srv.request.a = atoll(argv[1]);
  srv.request.b = atoll(argv[2]);

  if (client.call(srv))
  {
    ROS_INFO("Sum: %ld", (long int)srv.response.sum);
  }
  else
  {
    ROS_ERROR("Failed to call service add_two_ints");
    return 1;
  }

  return 0;
}

 

 

三、編譯節點

1、編輯beginner_tutorials 中的CMakeLists.txt文件，末尾加入

add_executable(add_two_ints_server src/add_two_ints_server.cpp)
target_link_libraries(add_two_ints_server ${catkin_LIBRARIES})
add_dependencies(add_two_ints_server beginner_tutorials_gencpp)

add_executable(add_two_ints_client src/add_two_ints_client.cpp)
target_link_libraries(add_two_ints_client ${catkin_LIBRARIES})
add_dependencies(add_two_ints_client beginner_tutorials_gencpp)

 

      這段代碼將生成兩個可執行程序"add_two_ints_server"和"add_two_ints_client"，這兩個可執行程序默認被放在你的devel space下的包目錄下，默認為~/catkin_ws/devel/lib/share/<package name>。你可以直接調用可執行程序，或者使用rosrun命令去調用它們

 

2、編譯

# In your catkin workspace
cd ~/catkin_ws
catkin_make

 

 

四、測試

1、運行Sevice

$ rosrun beginner_tutorials add_two_ints_server     (C++)

# 你將會看到如下類似的信息： 
Ready to add two ints.

 

 

2、運行Client

$ rosrun beginner_tutorials add_two_ints_client 1 3     (C++)

你將會看到如下類似的信息： 
request: x=1, y=3
sending back response: [4]
現在，你已經成功地運行了你的第一個Service和Client程序