目录

1、安装MQTT服务器

2、启动emqx，woesocket

3、编写服务端（发布）

4、编写客户端（订阅接收）

5、效果展示

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目的：前端接收mqtt消息，例如实时展示位置信息等。

1、安装MQTT服务器

可以使用网络提供的公共服务器也可以自建，例如这里安装EMQX。

下载 EMQX

输入emqx_ctl staus，出现以上说明已启动。 

2、 启动emqx，woesocket

输入本地emqx地址，例如http://127.0.0.1:18083/，打开websocket页面，确定好host，port等信息并启动，后续会用到这些信息。这实际上是个mqtt管理页面，后续连接到mqtt也能在该页面查看连接状态等信息。

3、编写服务端（发布）

这里用python写（实在是方便），语言不限。mqtt以及相关库自行安装。

#coding=utf-8
import paho.mqtt.client as mqtt
import random
import json

def on_connect(client,userdata,flags,rc):
    print("Connected with result code: "+str(rc))

def on_message(client,userdata,msg):
    print(msg.topic+" "+str(msg.payload))

client=mqtt.Client()
client.on_connect=on_connect
client.on_message=on_message
client.connect('你的ip',1883,600)

//这边模拟输出100个点位坐标（lon，lat，height）
for i in range(0,100):
    client.publish('你的topic',json.dumps({
    'lon':120+random.randint(0,2000)/2000,
    "lat":28+random.randint(0,2000)/2000,
    "height":random.randint(0,1000)/100
},ensure_ascii=False))

4、编写客户端（订阅接收）

 javascript编写客户端接受信息。

<script src="https://cdnjs.cloudflare.com/ajax/libs/paho-mqtt/1.0.1/mqttws31.min.js"></script>

<script>

        var hostname = '你的ip', 
            port = 8083, //这里就是第二步配置的port
            clientId = 'client-test',
            timeout = 5,
            keepAlive = 100,
            cleanSession = false,
            ssl = false,
            topic = '你的tpic';
        client = new Paho.MQTT.Client(hostname, port, clientId);
        //建立客户端实例  
        var options = {
            invocationContext: {
                host: hostname,
                port: port,
                path: client.path,
                clientId: clientId
            },
            timeout: timeout,
            keepAliveInterval: keepAlive,
            cleanSession: cleanSession,
            useSSL: ssl,
            // userName: userName,  
            // password: password,  
            onSuccess: onConnect,
            onFailure: function (e) {
                console.log(e);
                s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", onFailure()}";
                console.log(s);
            }
        };
        client.connect(options);
        //连接服务器并注册连接成功处理事件  
        function onConnect() {
            console.log("onConnected");
            s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", onConnected()}";
            console.log(s);
            client.subscribe(topic);
        }

        client.onConnectionLost = onConnectionLost;

        //注册连接断开处理事件  
        client.onMessageArrived = onMessageArrived;

        //注册消息接收处理事件  
        function onConnectionLost(responseObject) {
            console.log(responseObject);
            s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", onConnectionLost()}";
            console.log(s);
            if (responseObject.errorCode !== 0) {
                console.log("onConnectionLost:" + responseObject.errorMessage);
                console.log("连接已断开");
            }
        }

        function onMessageArrived(message) {
            s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", onMessageArrived()}";
            console.log(s);
            console.log("收到消息:" + message.payloadString);
        }

        function send() {
            var s = document.getElementById("msg").value;
            if (s) {
                s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", content:" + (s) + ", from: web console}";
                message = new Paho.MQTT.Message(s);
                message.destinationName = topic;
                client.send(message);
                document.getElementById("msg").value = "";
            }
        }

        var count = 0;

        function start() {
            window.tester = window.setInterval(function () {
                if (client.isConnected) {
                    var s = "{time:" + new Date().Format("yyyy-MM-dd hh:mm:ss") + ", content:" + (count++) +
                        ", from: web console}";
                    message = new Paho.MQTT.Message(s);
                    message.destinationName = topic;
                    client.send(message);
                }
            }, 1000);
        }

        function stop() {
            window.clearInterval(window.tester);
        }

        Date.prototype.Format = function (fmt) { //author: meizz 
            var o = {
                "M+": this.getMonth() + 1, //月份 
                "d+": this.getDate(), //日 
                "h+": this.getHours(), //小时 
                "m+": this.getMinutes(), //分 
                "s+": this.getSeconds(), //秒 
                "q+": Math.floor((this.getMonth() + 3) / 3), //季度 
                "S": this.getMilliseconds() //毫秒 
            };
            if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
            for (var k in o)
                if (new RegExp("(" + k + ")").test(fmt)) fmt = fmt.replace(RegExp.$1, (RegExp.$1.length == 1) ? (o[
                    k]) : (("00" + o[k]).substr(("" + o[k]).length)));
            return fmt;
        }
    </script>

5、效果展示