一.安装库 在Arduino的环境下使用MQTT在，我们需要下载一个库：PubSubClient 在git里面可以下载https://github.com/knolleary/pubsubclient
二.使用
1.说明 里面的代码其实是非常简洁明了的，基于C++。若是还是有不懂的，这有一个大佬有对pubsubclient进行过翻译：https://github.com/zy19970/Pubsubclient_API_document
2.连接 ①
首先将我们的库与代码放在同一级的目录下，然后引入头文件
#include "PubSubClient.h"②
创建两个类，但主要还是用PubSubClient的类
WiFiClient espClient;
PubSubClient client(espClient);
③
在初始化函数里写入我们的MQTT初始化代码：当然你还得自己写一个回调函数callback
client.setServer("MQTT server address", 1883);
client.setCallback(callback);
④
编写我们的连接/重连
判断是否连接成功使用：
client.connected()而连接的话，我们一般使用以下两种代码，connect被重写过。
client.connect(clientname,username,userkey) #如果mqtt服务器有域名的话，就使用这个
client.connect(clientname)⑤
重连函数优化一下就是这样
void reconnect()
{
while (!client.connected())
{
Serial.print("Attempting MQTT connection...");
String clientId = "ESP8266Client-";
clientId += String(random(0xffff), HEX);
if (client.connect(clientId.c_str(),username,key))
{
Serial.println("connected");
client.publish("fire", "hello world");
client.subscribe("fire");
}
else
{
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
delay(5000);
}
}
}⑥
CallBack函数的编写
void callback(char* topic, byte* payload, unsigned int length) {
//以下代码是将返回的消息用串口打印出来
Serial.print("Message arrived [");
Serial.print(topic);
Serial.print("] ");
for (int i = 0;
i < length;
i++)
{
Serial.print((char)payload[i]);
}
Serial.println();
//这里是收到消息的处理函数
if ((char)payload[0] == 'K')
{
Serial.println("yes");
}
else
{
Serial.println("no");
}
}⑦
主函数的编写
if (!client.connected())
{
reconnect();
}
client.loop();
3.发送消息
client.publish("topic", "text");
三.编译可用代码
#include
#include "PubSubClient.h"
#include const char* ssid = "1";
const char* password = "2";
const char* mqtt_server = "like xxxxx.mqtt.iot.gz.baidubce.com or ip";
const char* username = "4";
const char* key = "5";
long lastMsg = 0;
char msg[50];
int value = https://www.it610.com/article/0;
WiFiClient espClient;
PubSubClient client(espClient);
void setup_wifi()
{
delay(10);
Serial.print("Connecting to ");
Serial.println(ssid);
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();
if ((char)payload[0] == 'K') //这里是收到消息的处理函数
{
Serial.println("yes");
}
else
{
Serial.println("no");
}
}void reconnect()
{
while (!client.connected())
{
Serial.print("Attempting MQTT connection...");
String clientId = "ESP8266Client-";
clientId += String(random(0xffff), HEX);
if (client.connect(clientId.c_str(),username,key))
{
Serial.println("connected");
client.publish("fire", "hello world");
client.subscribe("fire");
}
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);
client.setCallback(callback);
}void loop()
{
if (!client.connected())
{
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 2000)
{
lastMsg = now;
++value;
}
} 【ESP8266学习记录4——连接(各种服务器商的)MQTT服务器(Arduino)】
