Mqtt
来自Jack's Lab
目录 |
1 Overview
MQTT是一个轻量的发布订阅模式消息传输协议,专门针对低带宽和不稳定网络环境的物联网应用设计。
MQTT官网: http://mqtt.org
MQTT V3.1.1协议规范: http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html
特点:
- 开放消息协议,简单易实现
- 发布订阅模式,一对多消息发布
- 基于TCP/IP网络连接
- 1字节固定报头,2字节心跳报文,报文结构紧凑
- 消息QoS支持,可靠传输保证
应用:
MQTT协议广泛应用于物联网、移动互联网、智能硬件、车联网、电力能源等领域。
- 物联网M2M通信,物联网大数据采集
- Android消息推送,WEB消息推送
- 移动即时消息,例如Facebook Messenger
- 智能硬件、智能家具、智能电器
- 车联网通信,电动车站桩采集
- 智慧城市、远程医疗、远程教育
- 电力、石油与能源等行业市场
2 Quickstart
MQTT 协议基于主题 (Topic) 进行消息路由
主题 (Topic) 类似 URL 路径,例如:
dev/gateway dev2srv/DEV1202 srv2dev/DEV1203
- 发布者通过主题 (Topic) 发送消息
- 所有订阅 (Subscribe) 该主题的订阅者,都会收到消息
主题 (Topic) 通过 '/' 分割层级,支持 '+', '#' 通配符:
'+': 表示通配一个层级,例如 a/+,匹配 a/x, a/y '#': 表示通配多个层级,例如 a/#,匹配 a/x, a/b/c
订阅者可以订阅含通配符主题,但发布者不允许向含通配符主题发布消息
3 Python Client
3.1 Install Python3
- Install python3.8 from https://www.python.org/downloads/
Install pip:
$ curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py $ sudo python get-pip.py
3.2 Install mqtt package
$ python3 --version Python 3.5.3rc1 $ pip3 install paho-mqtt Collecting paho-mqtt Downloading paho-mqtt-1.2.tar.gz (49kB) 100% |████████████████████████████████| 51kB 308kB/s Building wheels for collected packages: paho-mqtt Running setup.py bdist_wheel for paho-mqtt ... done Stored in directory: /home/comcat/.cache/pip/wheels/fa/db/fb/b495e37057e2f40534726b3c00ab26a58fc80fb8d17223df07 Successfully built paho-mqtt Installing collected packages: paho-mqtt Successfully installed paho-mqtt-1.2
More infor: https://pypi.python.org/pypi/paho-mqtt
3.3 mqtt client
import json import paho.mqtt.client as mqtt import sys # replace it to your id ########################################### mqtt_uname = 'test' mqtt_pass = 'test' devid = '12020030001' ########################################### def help_msg(): print("Supported cmd:") print("\tmqtt.py message") if len(sys.argv) >= 2: set_state = sys.argv[1] else: help_msg() sys.exit(-2) mqtt_tx_topic = 'dev/gw' mqtt_rx_topic = 'app2dev/' + devid mqtt_host = '192.168.1.97' mqtt_port = 1883 mqtt_msg = set_state def on_connect(client, u_dat, rc): if rc == 0: print("Connected successfully") else: print("Connection failed. rc = "+str(rc)) def on_publish(client, u_dat, rc): print("Message "+str(rc)+" published.") def on_subscribe(client, u_dat, mid, qos): print("Subscribe with "+str(mid)+" received") def on_message(client, udat, msg): print("Message received on topic "+msg.topic+" and payload "+str(msg.payload)) mqttc = mqtt.Client() mqttc.on_connect = on_connect mqttc.on_publish = on_publish mqttc.on_subscribe = on_subscribe mqttc.on_message = on_message mqttc.username_pw_set(mqtt_uname, mqtt_pass) mqttc.connect(mqtt_host, mqtt_port) mqttc.publish(mqtt_tx_topic, mqtt_msg)
4 Reference