物联网（ESP2866+MQTT+android）

准备：

1. 硬件：ESP8266(某宝)、ESP8266数据线（烧录软件）、杜邦线、面包板、无线路由器（有网）
2. 软件：Arduino IDE(官网)、android studio(官网)、EMQX(github)
3. 安装ESP8266开发板文件首选项添加8266附加管理器网址：http://arduino.esp8266.com/stable/package_esp8266com_index.json
4. 
5. 工具开发板管理器，输入8266
6. 
7. 安装下载（可能会很久、可能会失败很多次......）
8. 安装成功后可以在开发板选择：NodeMCU1.0(ESP-12E Module )
9. 安装arduion  PubSubClient库（项目-》加载库-》管理库搜索“PubSubClient”）安装

选择pubsubclient 示例（mqtt base）修改

1. 
   #include <ESP8266WiFi.h>
   #include <PubSubClient.h>const char* ssid = "TP-workS";              //修改
   const char* password = "HC201902";          //修改
   const char* mqtt_server = "........";   //修改 EMQX 服务地址WiFiClient espClient;
   PubSubClient client(espClient);
   unsigned long lastMsg = 0;
   #define MSG_BUFFER_SIZE  (50)
   char msg[MSG_BUFFER_SIZE];
   int value = 0;void setup_wifi() {delay(10);Serial.println();Serial.print("Connecting to ");Serial.println(ssid);WiFi.mode(WIFI_STA);WiFi.begin(ssid, password);while (WiFi.status() != WL_CONNECTED) {delay(500);Serial.print(".");}randomSeed(micros());Serial.println("");Serial.println("WiFi connected");Serial.println("IP address: ");Serial.println(WiFi.localIP());
   }void callback(char* topic, byte* payload, unsigned int length) {Serial.print("Message arrived [");Serial.print(topic);Serial.print("] ");for (int i = 0; i < length; i++) {Serial.print((char)payload[i]);}Serial.println();
   }void reconnect() {while (!client.connected()) {Serial.print("Attempting MQTT connection...");String clientId = "ESP8266Client-";clientId += String(random(0xffff), HEX);// Attempt to connectif (client.connect(clientId.c_str())) {Serial.println("connected");client.publish("outTopic", "hello world");     //发布 outTopic主题client.subscribe("inTopic");                   //订阅 inTopic主题} else {Serial.print("failed, rc=");Serial.print(client.state());Serial.println(" try again in 5 seconds");delay(5000);}}
   }void setup() {Serial.begin(115200);setup_wifi();client.setServer(mqtt_server, 1883);               //默认client.setCallback(callback);
   }void loop() {if (!client.connected()) {reconnect();}client.loop();unsigned long now = millis();if (now - lastMsg > 2000) {lastMsg = now;++value;snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);Serial.print("Publish message: ");Serial.println(msg);client.publish("outTopic", msg);}
   }

   启动EMQX 服务：进入EMQX解压bin路径：emqx start 启动 点击打开服务地址

   1. 在监控中（中文在设置 中可修改），即可看到（需新建监控主题：outTopic、inTopic）
   2.