ROS 笔记（08）— 服务数据的定义与使用

1. 服务模型

我们要实现的话题模型如下：

2. 自定义服务实现

2.1 定义 srv 文件

在功能包 service_client 目录下创建一个 srv 文件夹，在该文件夹中创建一个 Person.srv 文件，如下图所示：

Person.srv 中有我们自定义的消息格式

string name
uint8  age
uint8  sex

uint8 unknown = 0
uint8 male    = 1
uint8 female  = 2

---
string result

2.2 添加功能包依赖

在 package.xml 中添加以下 exec_depend 运行依赖：

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

2.3 添加编译选项

find_package(catkin REQUIRED COMPONENTS
  geometry_msgs
  rospy
  std_msgs
  turtlesim
  message_generation   # 新增内容

add_message_files(
   FILES
   Person.srv
 )

generate_messages(
   DEPENDENCIES
   std_msgs
 )

catkin_package(
# INCLUDE_DIRS include
# LIBRARIES topic_demo
   CATKIN_DEPENDS geometry_msgs rospy std_msgs turtlesim message_runtime
# DEPENDS system_lib
)

2.4 编译生成语言相关的文件

到项目根目录下执行 catkin_make 命令

$ catkin_make
Base path: /home/wohu/project/ros/ros_demo
Source space: /home/wohu/project/ros/ros_demo/src
Build space: /home/wohu/project/ros/ros_demo/build
Devel space: /home/wohu/project/ros/ros_demo/devel
Install space: /home/wohu/project/ros/ros_demo/install
####
#### Running command: "make cmake_check_build_system" in "/home/wohu/project/ros/ros_demo/build"
####
####
#### Running command: "make -j12 -l12" in "/home/wohu/project/ros/ros_demo/build"
####
[  0%] Built target std_msgs_generate_messages_nodejs
[  0%] Built target std_msgs_generate_messages_lisp
[  0%] Built target std_msgs_generate_messages_eus
[  0%] Built target std_msgs_generate_messages_cpp
[  0%] Built target std_msgs_generate_messages_py
[  0%] Built target _topic_demo_generate_messages_check_deps_Person
[  0%] Built target _service_client_generate_messages_check_deps_Person
[ 21%] Generating C++ code from service_client/Person.srv
[ 21%] Built target topic_demo_generate_messages_py
[ 28%] Generating Lisp code from service_client/Person.srv
[ 35%] Generating Python code from SRV service_client/Person
[ 42%] Built target topic_demo_generate_messages_lisp
[ 50%] Generating Javascript code from service_client/Person.srv
[ 57%] Generating EusLisp code from service_client/Person.srv
[ 71%] Built target topic_demo_generate_messages_eus
[ 78%] Built target topic_demo_generate_messages_nodejs
[ 85%] Built target topic_demo_generate_messages_cpp
[ 85%] Built target topic_demo_generate_messages
[ 85%] Built target service_client_generate_messages_lisp
[ 85%] Built target service_client_generate_messages_nodejs
[ 92%] Built target service_client_generate_messages_eus
[100%] Generating Python srv __init__.py for service_client
[100%] Built target service_client_generate_messages_cpp
[100%] Built target service_client_generate_messages_py
[100%] Built target service_client_generate_messages

可以看到会生成各种语言的代码文件。其中 Python 相关的代码文件在

/devel/lib/python2.7/dist-packages

目录下

2.5 运行代码

客户端代码 person_client.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# 该例程将请求/show_person服务，服务数据类型learning_service::Person

import sys
import rospy
from service_client.srv import Person, PersonRequest

def person_client():
	# ROS节点初始化
    rospy.init_node('person_client')

	# 发现/spawn服务后，创建一个服务客户端，连接名为/spawn的service
    rospy.wait_for_service('/show_person')
    try:
        person_client = rospy.ServiceProxy('/show_person', Person)

		# 请求服务调用，输入请求数据
        response = person_client("Tom", 20, PersonRequest.male)
        return response.result
    except rospy.ServiceException, e:
        print "Service call failed: %s"%e

if __name__ == "__main__":
	#服务调用并显示调用结果
    print "Show person result : %s" %(person_client())

服务端代码 person_server.py 代码

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# 该例程将执行/show_person服务，服务数据类型learning_service::Person

import rospy
from service_client.srv import Person, PersonResponse

def personCallback(req):
	# 显示请求数据
    rospy.loginfo("Person: name:%s age:%d sex:%d", req.name, req.age, req.sex)

	# 反馈数据
    return PersonResponse("OK")

def person_server():
	# ROS节点初始化
    rospy.init_node('person_server')

	# 创建一个名为/show_person的server，注册回调函数personCallback
    s = rospy.Service('/show_person', Person, personCallback)

	# 循环等待回调函数
    print "Ready to show person informtion."
    rospy.spin()

if __name__ == "__main__":
    person_server()

运行代码命令：

服务端代码：

$ cd  ~/catkin_ws
$ catkin_make 
$ source ./devel/setup.bash
$ rescore
$ rosrun service_client person_server.py 
Ready to show person informtion.
[INFO] [1655723144.945655]: Person: name:Tom  age:20  sex:1
[INFO] [1655723149.379382]: Person: name:Tom  age:20  sex:1
[INFO] [1655723150.891466]: Person: name:Tom  age:20  sex:1

客户端代码：

$ rosrun service_client person_client.py
response is result: "OK"
Show person result : OK