MQTT connection fails after a couple of days

Projects Networking, Protocols, and Devices
1

Hello, I'm playing with Home Assistant to automate my house and I'm building my own MQTT sensors/switches using an Arduino Duemilanove with Ethernet shield. The board runs fine for about a couple of days but after some time the connection to the broker fails and cannot be recovered until I reset Arduino.

The broker runs in my own LAN and it's the embedded one in HA.
My code is very simple:

#include <Ethernet.h>
#include <PubSubClient.h>

const char* mqtt_server = "192.168.1.100";
const char* mqtt_username = "myuser";
const char* mqtt_password = "mypassword";

EthernetClient ethClient;
PubSubClient client;
String clientId = "test";
uint8_t mac[6] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x06};
char msg[32];

const int pinIn[4]  = { 5, 6, 7, 8 };
const int pinOut[4] = { A0, A1, A2, A3 };

int oldIn[4];

void callback(char* topic, byte* payload, unsigned int length) {
  if (strlen(topic) > 17) return;
  if (strcmp(topic, "home/alarm/rele/1") == 0) 
  {    
    digitalWrite(pinOut[0], strncmp((char *)payload, "ON", 2));
    int val = bitRead(PORTC, 0);
    client.publish("home/alarm/rele/1/state", val ? "OFF" : "ON", true);
  }
}

void reconnect() {
  while (!client.connected()) 
  {
    Serial.print("Attempting MQTT connection...");
    if (client.connect(clientId.c_str(), mqtt_username, mqtt_password))
    {
      Serial.println("connected");
      client.subscribe("home/alarm/rele/+");
      break;
    } 
    else 
    {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
    }
    delay(5000);
  }
}

void setup() {
  for (int i = 0; i < 4; i++) 
  {
    pinMode(pinIn[i], INPUT_PULLUP);
    oldIn[i] = digitalRead(pinIn[i]);
    pinMode(pinOut[i], OUTPUT);
    digitalWrite(pinOut[i], HIGH);    
  }

  Serial.begin(115200);

  if (Ethernet.begin(mac) == 0) {
    Serial.println(F("Unable to configure Ethernet using DHCP"));
    for (;;);
  }

  Serial.println(F("Ethernet configured via DHCP"));
  Serial.print("IP address: ");
  Serial.println(Ethernet.localIP());
  Serial.println();

  client.setClient(ethClient);
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

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

  for (int i = 0; i < 4; i++) 
  {
    int val = digitalRead(pinIn[i]);
    if (val != oldIn[i])
    {
      oldIn[i] = val;
      char topic[32];
      sprintf(topic, "home/alarm/sensor/%u", i+1);
      client.publish(topic, val ? "ON" : "OFF", true);
    }
  }
}

Here a sample output:

Ethernet configured via DHCP
IP address: 192.168.1.224

Attempting MQTT connection...connected
...
[after some days]
...
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds
Attempting MQTT connection...failed, rc=-2 try again in 5 seconds

The value -2 is "MQTT_CONNECT_FAILED".
When this happens it won't reconnect anymore. But just resetting the Arduino leads to an immediate connection.

Given this behavior I guess the problem is on the Arduino side: do you see any evidence of mistakes in my code?

2

A quick look at your code and I cannot see any particular problem with it but maybe you should also check the Ethernet connection is up before checking if the MQTT connection is up as the problem might be there instead of the MQTT connection.
If your using DHCP then maybe the lease has expired and you need to reconnect or it's just a funny with the Ethernet connection.

I use ESP8266/ESP32 sensors and I have also had it where the WiFi router just stops accepting connections from a particular device or it drops connection.

Another thing to do might be to reset the Arduino in code if connection fails.

3

I didn't think about DHCP lease, I was thinking (wrongly) that is handled by the underlying library. I will check that. In any case your hints are useful because I focused only to the MQTT connection, but this one works on top of the Ethernet one... Hence I need to be sure the eth is up and running. Thanks a lot.