MQTTClient_Basic.ino

/****************************************************************************************************************************
  MQTTClient_Basic.ino - Dead simple MQTT Client

  For ESP8266/ESP32 AT-command running shields
  
  ESP8266_AT_WebServer is a library for the ESP8266/ESP32 AT-command shields to run WebServer
  Based on and modified from ESP8266 https://github.com/esp8266/Arduino/releases
  Built by Khoi Hoang https://github.com/khoih-prog/ESP8266_AT_WebServer
  Licensed under MIT license
 *****************************************************************************************************************************/

/*
  Basic MQTT example (without SSL!) with Authentication
  This sketch demonstrates the basic capabilities of the library.
  It connects to an MQTT server then:
  - providing username and password
  - publishes "hello world" to the topic "outTopic"
  - subscribes to the topic "inTopic", printing out any messages
    it receives. NB - it assumes the received payloads are strings not binary
    
  It will reconnect to the server if the connection is lost using a blocking
  reconnect function. See the 'mqtt_reconnect_nonblocking' example for how to
  achieve the same result without blocking the main loop.
*/

#include "defines.h"

#include <PubSubClient.h>

// Update these with values suitable for your network.
//const char* mqttServer = "broker.example";        // Broker address
const char* mqttServer = "broker.emqx.io";        // Broker address
//const char* mqttServer = "broker.shiftr.io";        // Broker address

const char *ID        = "MQTTClient_SSL-Client";  // Name of our device, must be unique
const char *TOPIC     = "MQTT_Pub";               // Topic to subcribe to
const char *subTopic  = "MQTT_Sub";               // Topic to subcribe to

//IPAddress mqttServer(172, 16, 0, 2);

int status = WL_IDLE_STATUS;      // the Wifi radio's status

void callback(char* topic, byte* payload, unsigned int length) 
{
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  
  for (unsigned int i = 0; i < length; i++) 
  {
    Serial.print((char)payload[i]);
  }
  
  Serial.println();
}

ESP8266_AT_Client  espClient;
PubSubClient    client(mqttServer, 1883, callback, espClient);

void reconnect()
{
  static String data = "Hello from MQTTClient_Basic on " + String(BOARD_NAME);
  
  // Loop until we're reconnected
  while (!client.connected())
  {
    Serial.print("Attempting MQTT connection to ");
    Serial.print(mqttServer);

    // Attempt to connect
    if (client.connect(ID, "try", "try"))
    {
      Serial.println("...connected");
      
      // Once connected, publish an announcement...
      client.publish(TOPIC, data.c_str());

      //Serial.println("Published connection message successfully!");
      //Serial.print("Subcribed to: ");
      //Serial.println(subTopic);
      
      client.subscribe(subTopic);
      // for loopback testing
      client.subscribe(TOPIC);
    }
    else
    {
      Serial.print("...failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void printWifiStatus()
{
  // print the SSID of the network you're attached to:
  // you're connected now, so print out the data
  Serial.print(F("You're connected to the network, IP = "));
  Serial.println(WiFi.localIP());

  Serial.print(F("SSID: "));
  Serial.print(WiFi.SSID());

  // print the received signal strength:
  int32_t rssi = WiFi.RSSI();
  Serial.print(F(", Signal strength (RSSI): "));
  Serial.print(rssi);
  Serial.println(F(" dBm"));
}

void setup()
{
  // Open serial communications and wait for port to open:
  Serial.begin(115200);
  while (!Serial && millis() < 5000);

  Serial.print(F("\nStarting MQTTClient_Basic on ")); Serial.print(BOARD_NAME);
  Serial.print(F(" with ")); Serial.println(SHIELD_TYPE); 
  Serial.println(ESP8266_AT_WEBSERVER_VERSION);

  // initialize serial for ESP module
  EspSerial.begin(115200);
  // initialize ESP module
  WiFi.init(&EspSerial);

  Serial.println(F("WiFi shield init done"));

  // check for the presence of the shield
  if (WiFi.status() == WL_NO_SHIELD)
  {
    Serial.println(F("WiFi shield not present"));
    // don't continue
    while (true);
  }

  // attempt to connect to WiFi network
  while ( status != WL_CONNECTED)
  {
    Serial.print(F("Connecting to SSID: "));
    Serial.println(ssid);
    // Connect to WPA/WPA2 network
    status = WiFi.begin(ssid, pass);
  }

  // you're connected now, so print out the data
  printWifiStatus();

  client.setServer(mqttServer, 1883);
  client.setCallback(callback);

  // Allow the hardware to sort itself out
  delay(1500);
}

#define MQTT_PUBLISH_INTERVAL_MS       10000L

String data         = "Hello from MQTTClient_Basic on " + String(BOARD_NAME) + " with " + String(SHIELD_TYPE);
const char *pubData = data.c_str();

unsigned long lastMsg = 0;

void loop() 
{
  static unsigned long now;
  
  if (!client.connected()) 
  {
    reconnect();
  }

  // Sending Data
  now = millis();
  
  if (now - lastMsg > MQTT_PUBLISH_INTERVAL_MS)
  {
    lastMsg = now;

    client.publish(TOPIC, pubData);
    
    Serial.print("Message Send : ");
    Serial.print(TOPIC);
    Serial.print(" => ");
    Serial.println(data);
  }
  
  client.loop();
}