ros使用service的所有步骤

1.生成头文件

• catkin_create_pkg msg_srv roscpp std_msgs
• cd msg_srv/
• mkdir srv
• roscp rospy_tutorials AddTwoInts.srv srv/AddTwoInts.srv

为了省事复制了一个，内容是：
int64 a
int64 b
—
int64 sum
其中的横线是三个短横线，上面是客户端发给服务端的消息类型，下面是服务端发给客户端的

• 在package.xml加

<build_depend>message_generation</build_depend>
<exec_depend>message_runtime</exec_depend>

• 修改CMakeLists.txt的若干行

find_package(catkin REQUIRED COMPONENTS roscpp rospy std_msgs message_generation)
catkin_package(
  ...
  CATKIN_DEPENDS message_runtime ...
  ...
)
add_service_files(
  FILES
  AddTwoInts.srv
)
generate_messages(
  DEPENDENCIES
  std_msgs
)

• cd …/…
• catkin_make --pkg msg_srv
• 生成的C++头文件将会放置在~/catkin_ws/devel/include/msg_srv/

2.服务端和客户端

• add_two_ints_server.cpp

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

bool add(msg_srv::AddTwoInts::Request  &req,
         msg_srv::AddTwoInts::Response &res)
{
   
  res.sum = req.a + req.b;
  ROS_INFO("request: x=%ld, y=%ld"