Mqtt+ardunio+esp8266 development (excluding mqtt server deployment)

Implementation preparation —MQTT agreement

Preface

1. PUBLISH – Release the news
Issuing message control message means that the client sends message to the server （ Or the server ） Transmit a message to the client .
2. SUBSCRIBE - Subscribe to topics
The client sends... To the server SUBSCRIBE The message is used to create one or more subscriptions . In order to forward the application message to the topic matching the subscription , The server will send PUBLISH Message to client .SUBSCRIBE The message also specifies for each subscription QoS Grade , The server will send messages to the client according to the level .
QoS Grade ：
a.QoS 0： The sender sends the message only once , No retry ,Broker No confirmation message will be returned . stay Qos0 Under the circumstances ,Broker May not have received the message .
b.QoS 1： The sender sends the message at least once , Make sure that the message arrives Broker,Broker A confirmation message needs to be returned PUBACK. stay Qos1 Under the circumstances ,Broker May receive duplicate messages .
c.QoS 2 ：Qos2 Use two-stage confirmation to ensure that messages are not lost and not repeated . stay Qos2 Under the circumstances ,Broker I'm sure I'll get a message , And only once .

If you want to know more MQTT For control message, please click ：MQTT Chinese agreement

General process ：

picture source ： A big man id:liefyuan

（ I would like to express my thanks to many leaders , Their articles helped me a lot ）

First step Software and hardware preparation

1.ESP8266 CP2102 Internet of things module

2. A number of male to female DuPont lines
3.arduino uno Development board or similar development board .
Software requirements ：
arduino ide
A physical picture ：
Pin connection ：
ESP8266 ------UNO
VCC-----------3.3v
GND----------GND
RX-------------TX　PIN2 （ With SoftWareSerialExample）
TX-------------RX　PIN3（ With SoftWareSerialExample）

Previously used 01TXRX It didn't work , I didn't expect that the soft serial communication was successfully solved .

pubsub Kuco and ESP8266 Development board / Libraries are used alone .
Steps are as follows ：
To install ESP8266 Development board （ Use Arduino 1.6.4+）：
- stay “ file -> Preferences -> Add development board manager website ” Add the following third web address ： http://arduino.esp8266.com/stable/package_esp8266com_index.json
- open “ Tools -> plate -> Board Manager ”, And then to ESP8266 single click “ install ”
- stay “ Tools -> Development board ” Choose from ESP8266

First step Distribution network + Connect

Come on ！ We use the library ！！！！MQTT There are many libraries , This article will use PubSubClient library . This library can be found in Arduino IDE Found in the library manager of . Tools -> Management of the library -> find PubSubClient Download according to the version you want , Then open the instance

(1） Connected to the Internet

A、ssid For yourself WIFI The name of the wireless network ,password by WIFI Wireless network password .

B、 utilize WiFi.begin(ssid, password); Connect to the Internet , This function is a function encapsulated in the library , Pass in two key values to connect .

C、 Connect to the network and then take out the connection status for judgment while (WiFi.status() != WL_CONNECTED) {…}

（2） Connect MQTT The server
A、 Define your own server address

B、client.setServer(mqtt_server, 1883); This wrapper function is used to connect MQTT The server ,1883 By default MQTT port

C、client.setCallback(callback); Set callback mode , When ESP8266 This method is called when a subscription message is received

The following is the soft serial port code ：10 and 11 It is the development board RX and TX Connect MQTT And ardunio

#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup()
{
    
// Open serial communications and wait for port to open:
Serial.begin(115200);
while (!Serial) {
    
; // wait for serial port to connect. Needed for Leonardo only
}
Serial.println("HELLO!JINYU");

// set the data rate for the SoftwareSerial port
mySerial.begin(115200);
mySerial.println("JINYU");
}

void loop() // run over and over
{
    
if (mySerial.available())
Serial.write(mySerial.read());
if (Serial.available())
mySerial.write(Serial.read());
}

The third step Subscribe and publish

（3） Subscribe and publish
A、 Instantiation
WiFiClient espClient;
PubSubClient client(espClient);
B、 Define subscription Topic :
const char* TOPIC = “”;
perhaps ：client.publish(“outTopic”, “hello world”);// Publish topics and content
client.subscribe(“inTopic”);// At the subscriber inTopic Subject matter .
C、 Serial port monitoring

At last, the general code is attached ：

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Update these with values suitable for your network.

const char* ssid = "JINYU";
const char* password = "150";
const char* mqtt_server = "123.57.133.**";// Here is the deployment MQTT Server address of the server 

WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup() {
    
  pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void setup_wifi() {
    

  delay(10);
  // We start by connecting to a WiFi network
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    
    delay(500);
    Serial.print(".");
  }

  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();

  // Switch on the LED if an 1 was received as first character
  if ((char)payload[0] == '1') {
    
    digitalWrite(BUILTIN_LED, LOW);   // Turn the LED on (Note that LOW is the voltage level
    // but actually the LED is on; this is because
    // it is acive low on the ESP-01)
  } else {
    
    digitalWrite(BUILTIN_LED, HIGH);  // Turn the LED off by making the voltage HIGH
  }

}

void reconnect() {
    
  // Loop until we're reconnected
  while (!client.connected()) {
    
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP8266Client")) {
    
      Serial.println("connected");
      // Once connected, publish an announcement...
      client.publish("outTopic", "hello world");
      // ... and resubscribe
      client.subscribe("inTopic");
    } else {
    
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}
void loop() {
    

  if (!client.connected()) {
    
    reconnect();
  }
  client.loop();

  long now = millis();
  if (now - lastMsg > 20000) {
    // Time delay 
    lastMsg = now;
    ++value;
    snprintf (msg, 75, "hello world #%ld", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("outTopic", msg);
  }

Wrong reflection ：
1、 My pin EN Pick up VCC It is not advisable to be normal VCC Pick up VCC
2、 If you use your own hotspot, don't use Chinese, it's easy to make mistakes
3、mqtt_server With ：8080
4、RX and TX Be sure to pay attention to the order
5、0 1 Sometimes you can't use , Soft serial port communication is required

If you use lot, Please refer to
id: A vegetarian pill that loves learning — As long as you can use a computer, you can understand the Internet of things tutorial （ Alibaba cloud +esp8266+ Wechat applet ）

My subscription debug information

Finishing up

At the end ： Endless learning , I will always be a brother hhhh