Golang使用mqtt

示例使用使用EMQX提供的免费公共 MQTT 服务器，该服务基于 EMQX 的 MQTT 物联网云平台 创建。服务器接入信息如下：

Broker: broker.emqx.io
TCP Port: 1883
Websocket Port: 8083

golang代码如下

package main

import (
	"fmt"
	mqtt "github.com/eclipse/paho.mqtt.golang"
	"time"
)

var messagePubHandler mqtt.MessageHandler = func(client mqtt.Client, msg mqtt.Message) {
	fmt.Printf("Received message: %s from topic: %s\n", msg.Payload(), msg.Topic())
}

var connectHandler mqtt.OnConnectHandler = func(client mqtt.Client) {
	fmt.Println("Connected")
}

var connectLostHandler mqtt.ConnectionLostHandler = func(client mqtt.Client, err error) {
	fmt.Printf("Connect lost: %v", err)
}

func main() {
	var broker = "broker.emqx.io" //地址
	var port = 1883  // 端口
	opts := mqtt.NewClientOptions()
	opts.AddBroker(fmt.Sprintf("tcp://%s:%d", broker, port))
	opts.SetClientID("go_mqtt_client111") //设备唯一id，正常应该是设备拿自己的设备id注册到服务器上。
	opts.SetUsername("emqx") //账号 
	opts.SetPassword("public") //密码
	opts.SetDefaultPublishHandler(messagePubHandler)
	opts.OnConnect = connectHandler
	opts.OnConnectionLost = connectLostHandler
	client := mqtt.NewClient(opts)
	if token := client.Connect(); token.Wait() && token.Error() != nil {
		panic(token.Error())
	}

	sub(client)     //等待消息
	publish(client) //发消息

	client.Disconnect(250)
}

func publish(client mqtt.Client) {
	num := 10
	for i := 0; i < num; i++ {
		text := fmt.Sprintf("Message %d", i)
		token := client.Publish("topic/test", 0, false, text)
		token.Wait()
		time.Sleep(time.Second)
	}
}

func sub(client mqtt.Client) {
	topic := "topic/test"
	token := client.Subscribe(topic, 1, nil) ////这里如果不指定方法，就用的上面的SetDefaultPublishHandler设置的方法
	token.Wait()
	fmt.Printf("Subscribed to topic: %s", topic)
}

输出

Connected
Subscribed to topic: topic/testReceived message: Message 0 from topic: topic/test
Received message: Message 1 from topic: topic/test
Received message: Message 2 from topic: topic/test
Received message: Message 3 from topic: topic/test
Received message: Message 4 from topic: topic/test
.....