python使用MQTT给硬件传输图片的实现方法

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：

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：

反馈：BASE---------> Web服务器:

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：

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')

总结

以上所述是小编给大家介绍的python使用MQTT给硬件传输图片的实现方法,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！
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