任务简述
最近因需要用python写一个微服务来用MQTT给硬件传输图片，其中python用的是flask框架，大概流程如下：
image
协议为：
需要将图片数据封装成多个消息进行传输，每个消息传输的数据字节数为1400Byte。
消息(MQTT Payload) 格式：Web服务器-------->BASE：
image
反馈：BASE---------> Web服务器:
image
如果Web服务器发送完一个“数据传输消息”后，5S内没有收到MQTT“反馈消息”或者收到的反馈中显示“数据包不完整”，则重发该“数据传输消息”。
程序流程图
根据上面的协议，可以得到如下的流程图：
image
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代码如下：
# encoding:utf-8
from flask import Flask, jsonify
from flask_restful import Api, Resource, reqparse
from PIL import Image
from io import BytesIO
import requests
import os, logging, time
import paho.mqtt.client as mqtt
import struct
from flask_cors import *
# 日志配置信息
logging.basicConfig(
level=logging.INFO,
format='%(asctime)s - %(name)s - %(levelname)s - %(message)s （runing by %(funcName)s',
)
class Mqtt(object):
def __init__(self, img_data, size):
self.MQTTHOST = '*******'
self.MQTTPORT = "******"
# 订阅和发送的主题
self.topic_from_base = 'mqttTestSub'
self.topic_to_base = 'mqttTestPub'
self.client_id = time.strftime('%Y%m%d%H%M%S', time.localtime(time.time()))
self.client = mqtt.Client(self.client_id)
# 完成链接后的回掉函数
self.client.on_connect = self.on_connect
# 图片大小
self.size = size
# 用于跳出死循环，结束任务
self.finished = None
# 包的编号
self.index = 0
# 将收到的图片数据按大小分成列表
self.image_data_list = [img_data[x:x + 1400] for x in range(0, self.size, 1400)]
# 记录发布后的数据，用于监控时延
self.pub_time = 0
self.header_to_base = 0xffffeeee
self.header_from_base = 0xeeeeffff
# 功能标识
self.function_begin = 0x01
self.function_doing = 0x02
self.function_finished = 0x03
# 包的完整和非完整状态
self.whole_package = 0x01
self.bad_package = 0x00
# 头信息的格式,小端模式
self.format_to_base = "<Lbhh"
self.format_from_base = "<Lbhb"
# 如果重发包时，用于检查是否重发第一个包
self.first = True
# 如果重发包时，用于检查是否重发最后一个包
self.last = False
self.begin_data = 'image.jpg;' + str(self.size)
# 链接mqtt服务器函数
def on_mqtt_connect(self):
self.client.connect(self.MQTTHOST, self.MQTTPORT, 60)
self.client.loop_start()
# 链接完成后的回调函数
def on_connect(self, client, userdata, flags, rc):
logging.info("+++ Connected with result code {} +++".format(str(rc)))
self.client.subscribe(self.topic_from_base)
# 订阅函数
def subscribe(self):
self.client.subscribe(self.topic_from_base, 1)
# 消息到来处理函数
self.client.on_message = self.on_message
# 接收到信息后的回调函数
def on_message(self, client, userdata, msg):
# 如果接受第一个包则不需要重发第一个
self.first = False
# 将接受到的包进行解压，得到一个元组
base_tuple = struct.unpack(self.format_from_base, msg.payload)
logging.info("+++ imageData's letgth is {}, base_tupe is {} +++".format(self.size, base_tuple))
logging.info("+++ package_number is {}, package_status_from_base is {} +++"
.format(base_tuple[2], base_tuple[3]))
# 检查接受到信息的头部是否正确
if base_tuple[0] == self.header_from_base:
logging.info("+++ function_from_base is {} +++".format(base_tuple[1]))
# 是否完成传输，如果完成则退出
if base_tuple[1] == self.function_finished:
logging.info("+++ finish work +++")
self.finished = 1
self.client.disconnect()
else:
# 是否是最后一个包
if self.index == len(self.image_data_list) - 1:
self.publish('finished', self.function_finished)
self.last = True
logging.info("+++ finished_data_to_base is finished+++")
else:
# 如果接收到的包不是 0x03则进行传送数据
if base_tuple[1] == self.function_begin or base_tuple[1] == self.function_doing:
logging.info("+++ package_number is {}, package_status_from_base is {} +++"
.format(base_tuple[2],base_tuple[3]))
# 如果数据的反馈中，包的状态是1则继续发下一个包
if base_tuple[3] == self.whole_package:
self.publish(self.index, self.function_doing)
logging.info("+++ data_to_base is finished+++")
self.index += 1
# 如果数据的反馈中，包的状态是0则重发数据包
elif base_tuple[3] == self.bad_package:
re_package_number = base_tuple[2]
self.publish(re_package_number-1, self.function_doing)
logging.info("+++ re_data_to_base is finished+++")
else:
logging.info("+++ package_status_from_base is not 0 or 1 +++")
self.client.disconnect()
else:
logging.info("+++ function_identifier is illegal +++")
self.client.disconnect()
else:
logging.info("+++ header_from_base is illegal +++")
self.client.disconnect()
# 数据发送函数
def publish(self, index, fuc):
# 看是否是最后一个包
if index == 'finished':
length = 0
package_number = 0
data = b''
else:
length = len(self.image_data_list[index])
package_number = index
data = self.image_data_list[index]
# 打包数据头信息
buffer = struct.pack(
self.format_to_base,
self.header_to_base,
fuc,
package_number,
length
)
to_base_data = buffer + data
# mqtt发送
self.client.publish(
self.topic_to_base,
to_base_data
)
self.pub_time = time.time()
# 发送第一个包函数
def publish_begin(self):
buffer = struct.pack(
self.format_to_base,
self.header_to_base,
self.function_begin,
0,
len(self.begin_data.encode('utf-8')),
)
begin_data = buffer + self.begin_data.encode('utf-8')
self.client.publish(self.topic_to_base, begin_data)
# 控制函数
def control(self):
self.on_mqtt_connect()
self.publish_begin()
begin_time = time.time()
self.pub_time = time.time()
self.subscribe()
while True:
time.sleep(1)
# 超过5秒重传
date = time.time() - self.pub_time
if date > 5:
# 是否重传第一个包
if self.first == True:
self.publish_begin()
logging.info('+++ this is timeout first_data +++')
# 是否重传最后一个包
elif self.last == True:
self.publish('finished', self.function_finished)
logging.info('+++ this is timeout last_data +++')
else:
self.publish(self.index-1, self.function_doing)
logging.info('+++ this is timeout middle_data +++')
if self.finished == 1:
logging.info('+++ all works is finished+++')
break
print(str(time.time()-begin_time) + 'begin_time - end_time')
app = Flask(__name__)
api = Api(app)
CORS(app, supports_credentials=True)
# 接受参数
parser = reqparse.RequestParser()
parser.add_argument('url', help='mqttImage url', location='args', type=str)
class GetImage(Resource):
# 得到参数并从图床下载到本地
def get(self):
args = parser.parse_args()
url = args.get('url')
response = requests.get(url)
# 获取图片
image = Image.open(BytesIO(response.content))
# 存取图片
add = os.path.join(os.path.abspath(''), 'image.jpg')
image.save(add)
# 得到图片大小
size = os.path.getsize(add)
f = open(add, 'rb')
imageData = f.read()
f.close()
# 进行mqtt传输
mqtt = Mqtt(imageData, size)
mqtt.control()
# 删除文件
os.remove(add)
logging.info('*** the result of control is {} ***'.format(1))
return jsonify({
"imageData": 1
})
api.add_resource(GetImage, '/image')
if __name__ == '__main__':
app.run(debug=True, host='0.0.0.0')
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