基于node.js搭建简单的MQTT服务器，手机通过热点连接电脑实现MQTT服务器测试

服务器搭建

首先搭建好node.js环境，配置好MQTT服务器，这个网上教程有许多，可以参照这篇博客来进行配置。

服务端mqtt.js:

const mosca = require("mosca");
const MqttServer = new mosca.Server({
  port: 1883
});
MqttServer.on("clientConnected", function(client) {
  //当有客户端连接时的回调.
  console.log("client connected", client.id);
});
/**
 * 监听MQTT主题消息
 * 当客户端有连接发布主题消息时
 **/
MqttServer.on("published", function(packet, client) {
  var topic = packet.topic;
  switch (topic) {
    case "test":
      // console.log('message-publish', packet.payload.toString());
      //MQTT可以转发主题消息至其他主题
      //MqttServer.publish({ topic: 'other', payload: 'sssss' });
      break;
    case "other":
      console.log("message-123", packet.payload.toString());
      break;
  }
});

MqttServer.on("ready", function() {
  //当服务开启时的回调
  console.log("mqtt is running...");
});

客户端发送方publish.js

const mqtt = require("mqtt");
const client = mqtt.connect("mqtt://192.168.137.1 :1883"); //连接到mqtt服务端
setInterval(function() {
  const value = Math.ceil(Math.random() * 40);
  client.publish("test", value.toString(), { qos: 0, retain: true });
}, 3000);

客户端订阅方subscribe.js

const mqtt = require("mqtt");
// const mqtt = require('./node_modules/mqtt/dist/mqtt.min.js')
const client = mqtt.connect("mqtt://192.168.137.1 :1883"); //指定服务端地址和端口
client.on("connect", function() {
  console.log("服务器连接成功");
  // connected = client.connected
  client.subscribe("test", { qos: 0}); //订阅主题为test的消息
});
client.on("message", function(top, message) {
  console.log("当前topic：", top);
  console.log("收到消息：", message.toString());
});