ROS series: service communication (2)

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foreword

Learning record, error summary

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1. Service communication (python)

Done with python.

2. Use steps

1. Server

The code is as follows (example):

#! /usr/bin/env python
import rospy 

from plumbing_server_client.srv import AddInts,AddIntsRequest,AddIntsResponse
"""
服务段：解析客户端的请求，产生响应
1、导包
2、初始化节点
3、创建服务端的对象
4、处理逻辑（回调函数） 发生时间不确定用回调函数
5、回调函数必带spin（）

"""
def doNum(request):
    # 解析提交的两个整数
    num1 = request.num1
    num2 = request.num2
    # 求和
    sum = num1+num2
    # 将结果封装进响应
    response = AddIntsResponse()     # 创建一个response对象类型是AddIntsResponse
    response.sum = sum
    rospy.loginfo("服务器接收到的请求数据是：num1=%d,num2=%d，响应结果是sum=%d",num1,num2,sum)
    return response

if __name__=="__main__":
    #2、初始化节点
    rospy.init_node("heiShui")
    # 3、创建服务端的对象
    server=rospy.Service("addInts",AddInts,doNum)
    rospy.loginfo("服务器启动成功")
    # 4、处理逻辑（回调函数） 发生时间不确定用回调函数
    # 5、回调函数必带spin（）
    rospy.spin()

2. Client

The code is as follows (example):

#! /usr/bin/env python
from http import client
from urllib import response
import rospy 

from plumbing_server_client.srv import AddInts,AddIntsRequest,AddIntsResponse
"""
客户端：发出请求，处理服务端响应
1、导包
2、初始化节点
3、创建客户端的对象
4、发出请求
5、处理响应

"""
if __name__=="__main__":
    rospy.init_node("erHei")
    client =rospy.ServiceProxy("addInts",AddInts)
    response=client.call(1,2)   #call函数会返回一个值用response接收它
    rospy.loginfo("响应的数据是%d",response.sum)

3. Running results

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Summarize

Error 1:

"/home/wht/at_demo/demo03_ws/src/plumbing_server_client/scripts/demo02_client_p.py", 第20行, in <module>.
    rospy.loginfo("响应的数据是%d", response.sum)
AttributeError: 模块'urllib.response'没有属性'sum'。

Error analysis: because the function usage of client.call is not understood, it will return a value, which should be received by response, and its fields should be printed by rospy.loginfo: response=client.call(1,2)
learn 1: add sys file

It can be realized, dynamic input;
learning 2: the client hang function is not consistent with the c++ version;