ROS notes (08) - definition and use of service data

1. Service model

The topic model we want to implement is as follows ：

2. Custom service implementation

2.1 Definition srv file

In Feature Pack service_client Create one in the directory srv Folder , Create a... In this folder Person.srv file , As shown in the figure below ：

Person.srv There is our custom message format in

string name
uint8  age
uint8  sex

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

---
string result

2.2 Add Feature Pack dependencies

stay package.xml Add the following exec_depend Operational dependency ：

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

2.3 Add compile options

find_package(catkin REQUIRED COMPONENTS
  geometry_msgs
  rospy
  std_msgs
  turtlesim
  message_generation   #  The new content 

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 Compile and generate language related files

To the root directory of the project catkin_make command

$ 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

You can see that code files in various languages will be generated . among Python The relevant code files are in

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

Under the table of contents

2.5 Run code

Client code person_client.py

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

#  The routine will request /show_person service , Service data type learning_service::Person

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

def person_client():
	# ROS Node initialization 
    rospy.init_node('person_client')

	#  Find out /spawn After service , Create a service client , The connection name is /spawn Of service
    rospy.wait_for_service('/show_person')
    try:
        person_client = rospy.ServiceProxy('/show_person', Person)

		#  Request service call , Enter request data 
        response = person_client("Tom", 20, PersonRequest.male)
        return response.result
    except rospy.ServiceException, e:
        print "Service call failed: %s"%e

if __name__ == "__main__":
	# The service calls and displays the call result 
    print "Show person result : %s" %(person_client())

Server code person_server.py Code

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

#  The routine will execute /show_person service , Service data type learning_service::Person

import rospy
from service_client.srv import Person, PersonResponse

def personCallback(req):
	#  Display request data 
    rospy.loginfo("Person: name:%s age:%d sex:%d", req.name, req.age, req.sex)

	#  Feedback data 
    return PersonResponse("OK")

def person_server():
	# ROS Node initialization 
    rospy.init_node('person_server')

	#  Create a file called /show_person Of server, Register callback function personCallback
    s = rospy.Service('/show_person', Person, personCallback)

	#  Loop waiting for callback function 
    print "Ready to show person informtion."
    rospy.spin()

if __name__ == "__main__":
    person_server()

Run the code command ：

Server code ：

$ 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

Client code ：

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