基于ROS 服务通信模式详解

int64 a
int64 b
---
int64 sum

/**
 * AddTwoInts Server
 */

#include "ros/ros.h"
#include "learning_communication/AddTwoInts.h"

// service回调函数，输入参数req，输出参数res
bool add(learning_communication::AddTwoInts::Request &req,
     learning_communication::AddTwoInts::Response &res)
{
  // 将输入参数中的请求数据相加，结果放到应答变量中
  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节点初始化
  ros::init(argc, argv, "add_two_ints_server");

  // 创建节点句柄
  ros::NodeHandle n;

  // 创建一个名为add_two_ints的server，注册回调函数add()
  ros::ServiceServer service = n.advertiseService("add_two_ints", add);

  // 循环等待回调函数
  ROS_INFO("Ready to add two ints.");
  ros::spin();

  return 0;
}

/**
 * AddTwoInts Client
 */

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

int main(int argc, char **argv)
{
  // ROS节点初始化
  ros::init(argc, argv, "add_two_ints_client");

  // 从终端命令行获取两个加数
  if (argc != 3)
  {
    ROS_INFO("usage: add_two_ints_client X Y");
    return 1;
  }

  // 创建节点句柄
  ros::NodeHandle n;

  // 创建一个client，请求add_two_int service
  // service消息类型是learning_communication::AddTwoInts
  ros::ServiceClient client = n.serviceClient<learning_communication::AddTwoInts>("add_two_ints");

  // 创建learning_communication::AddTwoInts类型的service消息
  learning_communication::AddTwoInts srv;
  srv.request.a = atoll(argv[1]);
  srv.request.b = atoll(argv[2]);

  // 发布service请求，等待加法运算的应答结果
  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;
}

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

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

<?xml version="1.0"?>
<package>
 <name>learning_communication</name>
 <version>0.0.0</version>
 <description>The learning_communication package</description>
 <maintainer email="hcx@todo.todo">hcx</maintainer>

 <license>TODO</license>

 <buildtool_depend>catkin</buildtool_depend>
 <build_depend>geometry_msgs</build_depend>
 <build_depend>roscpp</build_depend>
 <build_depend>rospy</build_depend>
 <build_depend>std_msgs</build_depend>
 <run_depend>geometry_msgs</run_depend>
 <run_depend>roscpp</run_depend>
 <run_depend>rospy</run_depend>
 <run_depend>std_msgs</run_depend>

 <build_depend>message_generation</build_depend>
 <run_depend>message_runtime</run_depend>


 <!-- The export tag contains other, unspecified, tags -->
 <export>
  <!-- Other tools can request additional information be placed here -->

 </export>
</package>

1）config：放置功能包中的配置文件，由用户创建，文件名可以不同。
2）include：放置功能包中需要用到的头文件。
3）scripts：放置可以直接运行的Python脚本。
4）src：放置需要编译的C++代码。
5）launch：放置功能包中的所有启动文件。
6）msg：放置功能包自定义的消息类型。
7）srv：放置功能包自定义的服务类型。
8）action：放置功能包自定义的动作指令。
9）CMakeLists.txt：编译器编译功能包的规则。

message_generation 
message_runtime

find_package(catkin REQUIRED COMPONENTS 
geometry_msgs 
roscpp 
rospy 
std_msgs 
message_generation 
)

add_service_files( 
FILES 
AddTwoInts.srv 
) 

#include "learning-communication/AddTwoInts.h"

bool add(learning_communication::AddTwoInts::Request &req,learning_communication::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);
ROS_INFO("sending back response: [%ld]", (long int)res.sum);
return true;
}

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

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

add_executable(server src/server.cpp)
target_link_libraries(server ${catkin_LIBRARIES})
add_dependencies(server ${PROJECT_NAME}_gencpp)
add_executable(client src/client.cpp)
target_link_libraries(client ${catkin_LIBRARIES})
add_dependencies(client ${PROJECT_NAME}_gencpp)

rosservice list     输出可用服务的信息
rosservice call     调用带参数的服务
rosservice type     输出服务类型
rosservice find     依据类型寻找服务find services by service type
rosservice uri     输出服务的ROSRPC uri