I'm using Nodemcu-32S as MQTT Client for connecting with an MQTT broker. The broker is
EMQ X, it is hosted in VPS (Windows Server 2016, 4 core, 8GB Ram).
The
problem is, MQTT broker sends last will message within 10 to 20 seconds
of connecting to the server, while the client is still connected and
publishing and subscribing data properly.
Last will message topic is "Connection/online".
When the Nodemcu-32S is connected, it publishes, "// 1234 1 12:10:25T121020//"
When the Nodemcu-32S ungracefully disconnected like power or network failure , it publishes, "// 1234 0 12:10:25T121020//"
My code is :
#include <Wire.h>
#include "SH1106Wire.h"
#include <WiFi.h>
#include <PubSubClient.h>
const char* ssid = "*******";
const char* password = "******";
//******************* Time Settings ******************************
const char* ntpServer = "pool.ntp.org";
const long gmtOffset_sec = 21600;
const int daylightOffset_sec = 0; // no need for dhaka
char time_stmp[50];
//************************* MQTT Settings ***************************
const char* mqtt_server = "207.***.232.***";
WiFiClient espClient;
PubSubClient client(espClient);
long lastMsg = 0;
char msg[100];
int value = 0;
char dev_id[]="DEV_002";
byte willQoS = 1;
const char willTopic[] = "Connection/online";
//const char willTopic[] = "$SYS/brokers/node1/clients/clientid1/disconnected";
char willMessage[50];
boolean willRetain = false;
char txt[50]; // for reply
//********************************** OLED *******************************************
SH1106Wire display(0x3c, 21, 22); // ADDRESS, SDA, SCL , NODEMCU-32S ESP32
//***********************************************************************************
void print_LocalTime()
{
struct tm timeinfo;
if(!getLocalTime(&timeinfo))
{
Serial.println("Failed to obtain time");
return;
}
strftime(time_stmp, sizeof(time_stmp), "%H:%M:%ST%d.%m.%y", &timeinfo);
}
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(".");
}
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();
// Switch on the LED if an 1 was received as first character
if (strcmp(topic,"esp_out")==0)
{
// whatever you want for this topic
if ((char)payload[0] == '1')
{
digitalWrite(2, HIGH); // Turn the LED on (Note that LOW is the voltage level
// but actually the LED is on; this is because
// it is active low on the ESP-01)
}
if ((char)payload[0] == '2')
{
digitalWrite(2, LOW); // Turn the LED off by making the voltage HIGH
}
}
}
void reconnect()
{
// Loop until we're reconnected
while (!client.connected())
{
Serial.print("Attempting MQTT connection...");
//String clientId = "ESP8266Client-";
String clientId = "1234";
//clientId += String(random(0xffff), HEX);
// Attempt to connect
//if (client.connect(clientId.c_str()))
print_LocalTime();
snprintf (willMessage, sizeof(willMessage), "// %s 0 %s//",clientId,time_stmp);
//boolean rc= client.connect(clientId.c_str(), willTopic, willQoS, willRetain, willMessage);
if (client.connect(clientId.c_str(), willTopic, willQoS, willRetain, willMessage))
{
Serial.println("connected");
// Once connected, publish an announcement...
snprintf (txt, sizeof(txt), "// %s 1 %s//",clientId,time_stmp);
boolean rcc = client.publish(willTopic, txt);
if ( rcc)
{
Serial.print(willTopic);
Serial.print(" : ");
Serial.print(txt);
Serial.println(" Oaky");
}
else
Serial.println(" Online Status publish error");
// ... and resubscribe
client.subscribe("esp_out");
}
else
{
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" try again in 5 seconds");
// Wait 5 seconds before retrying
delay(5000);
}
}
}
void setup()
{
pinMode(2, OUTPUT); // buzzer
Serial.begin(115200);
delay(100);
display.init();
display.flipScreenVertically();
//display.setFont(ArialMT_Plain_10);
delay(100);
display.clear();
setup_wifi();
delay(100);
configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
print_LocalTime();
delay(100);
client.setServer(mqtt_server, 1883);
client.setCallback(callback);
//logo_print();
}
void loop()
{
if (!client.connected()) {
reconnect();
}
client.loop();
long now = millis();
if (now - lastMsg > 500)
{
lastMsg = now;
++value;
snprintf (msg, 100, "hello world #%ld", value);
Serial.print("Publish message: ");
Serial.println(msg);
client.publish("esp_in", msg);
}
}
The last will message, "// 1234 0 12:10:25T121020//" , is supposed to be
published in topic "Connection/online", if the NOdemcu-32S MQTT client
is disconnected ungracefully. But this message is published while the
client is still connected, and publishing and subscribing data properly.