• step1
  到目标package下
  mkdir srv
  创建一个srv文件

  
  

• step2
  修改CMakeLists.txt

  
  
  
  
  
  
  
  

• step3
  修改package.xml
  添加这两句

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

• step4
  到工作空间目录下
  catkin_make

  
  

在Python中call一个service

import rospy
from gazebo_msgs.srv import DeleteModel ,DeleteModelRequest
from roscpp.srv import GetLoggers,GetLoggersRequest
import sys

rospy.init_node('service_client')
rospy.wait_for_service('/gazebo/delete_model')
delete_model_service=rospy.ServiceProxy('/gazebo/delete_model',DeleteModel)
kk=DeleteModelRequest()
kk.model_name="unit_box"
result=delete_model_service(kk)
print(result)

rospy.wait_for_service('gazebo_gui/get_loggers')
get_loggers_service=rospy.ServiceProxy('gazebo_gui/get_loggers',GetLoggers)
# gg=GetLoggersRequest()
result=get_loggers_service()
print('get Result:\n{}'.format(result))

上面这段代码是两个例子，一个是GAZEBO删除模型，一个是/rosout/get_loggers

首先是检查service是否可用，wait_for_service 的作用如下：

Blocks until service is available. Use this in initialization code if your program depends on a service already running

如果你的service需要request的话，就要import <你的service的名字>Request
然后使用它。

写一个service server

上面我们加了一个srv文件，现在我们来为它写一个service server。
这个srv需要传入一个float64，一个int32，然后执行一系列操作后返回成功或失败（这个例子里只有True）
具体来说就是让turtlesim里的小海龟画一个正方形，radius是这个正方形的边长，repetitions决定走几遍。

#! /usr/bin/env python
import rospy
from test_package.srv import my_custom_service_message,my_custom_service_messageRequest,my_custom_service_messageResponse
from geometry_msgs.msg import Twist
from math import radians

def my_cus_callback(req):
    print(req.radius)
    print(req.repetitions)
    turtle1_draw_square(req.radius,req.repetitions)
    return my_custom_service_messageResponse(True)

def turtle1_draw_square(radius,repetitions):
    pub = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
    rate = rospy.Rate(10)
    move_cmd = Twist()
    move_cmd.linear.x = radius
    turn_cmd = Twist()
    turn_cmd.angular.z = radians(90)
    print('go forward')
    for rep in range(repetitions):
        for i in range(4):
            for x in range(20):
                pub.publish(move_cmd)
                rate.sleep()
            print('turn right')
            for z in range(10):
                pub.publish(turn_cmd)
                rate.sleep()

rospy.init_node('service_server')
my_cus_service=rospy.Service('my_cus_service',my_custom_service_message,my_cus_callback)
rospy.spin()