第16章 客户端开发实战
16.1 Python客户端
安装
pipinstallpaho-mqtt
基础示例
importpaho.mqtt.clientasmqttdefon_connect(client,userdata,flags,rc):print(f"Connected:{rc}")client.subscribe("sensor/#")defon_message(client,userdata,msg):print(f"{msg.topic}:{msg.payload.decode()}")client=mqtt.Client()client.on_connect=on_connect client.on_message=on_message client.connect("localhost",1883,60)client.loop_forever()
发布示例
importpaho.mqtt.clientasmqttimportjsonimporttime client=mqtt.Client()client.connect("localhost",1883,60)whileTrue:data={'temperature':25.5,'humidity':60.2,'timestamp':time.time()}client.publish("sensor/data",json.dumps(data),qos=1)time.sleep(5)
16.2 JavaScript/Web客户端
安装
npminstallmqtt
示例
constmqtt=require('mqtt');constclient=mqtt.connect('mqtt://localhost:1883');client.on('connect',()=>{console.log('Connected');client.subscribe('sensor/#');});client.on('message',(topic,message)=>{console.log(topic,message.toString());});// 发布setInterval(()=>{client.publish('sensor/data',JSON.stringify({temp:Math.random()*30}));},5000);
WebSocket连接
<scriptsrc="https://unpkg.com/mqtt/dist/mqtt.min.js"></script><script>constclient=mqtt.connect('ws://localhost:9001');client.on('connect',()=>{client.subscribe('home/#');});client.on('message',(topic,message)=>{console.log(topic,message.toString());});</script>
16.3 Java客户端
Maven依赖
<dependency><groupId>org.eclipse.paho</groupId><artifactId>org.eclipse.paho.client.mqttv3</artifactId><version>1.2.5</version></dependency>
示例
importorg.eclipse.paho.client.mqttv3.*;publicclassMQTTClient{publicstaticvoidmain(String[]args){try{MqttClientclient=newMqttClient("tcp://localhost:1883",MqttClient.generateClientId());MqttConnectOptionsoptions=newMqttConnectOptions();options.setCleanSession(true);options.setAutomaticReconnect(true);client.setCallback(newMqttCallback(){publicvoidmessageArrived(Stringtopic,MqttMessagemessage){System.out.println(topic+": "+message);}publicvoiddeliveryComplete(IMqttDeliveryTokentoken){}publicvoidconnectionLost(Throwablecause){}});client.connect(options);client.subscribe("sensor/#");// 保持运行Thread.sleep(Long.MAX_VALUE);}catch(Exceptione){e.printStackTrace();}}}
16.4 C/C++客户端
安装
# Ubuntusudoaptinstalllibmosquitto-dev# CentOSsudoyuminstallmosquitto-devel
示例
#include<mosquitto.h>#include<stdio.h>#include<stdlib.h>#include<string.h>voidon_message(structmosquitto*mosq,void*obj,conststructmosquitto_message*message){printf("%s: %s\n",message->topic,(char*)message->payload);}intmain(){structmosquitto*mosq=NULL;mosquitto_lib_init();mosq=mosquitto_new("publisher",true,NULL);mosquitto_connect(mosq,"localhost",1883,60);mosquitto_publish(mosq,NULL,"test",6,"hello",0,false);mosquitto_loop_start(mosq);sleep(1);mosquitto_loop_stop(mosq,false);mosquitto_destroy(mosq);mosquitto_lib_cleanup();return0;}
