Hi @Guillermo-Schimmel,
I know it's closed but just noticed this issue, you most probably had STP (Spanning Tree Protocol) enabled on that port, which is normal for ent switch, and while it waits for a loop it blocks trafic from that port.
Disabling that feature should solve this problem.

I think I'm ussing the latest one

but as you said I don't think it will fix my issue though.
But looking at the examples I found that they have a connect function which then can be used to reconnect whenever needed not constantly like it happens now,

But not sure how I could integrate that functionality in this sketch though, as I'm not that experienced with programming
To you think it will be possible?

/*
 Reconnecting MQTT example - non-blocking

 This sketch demonstrates how to keep the client connected
 using a non-blocking reconnect function. If the client loses
 its connection, it attempts to reconnect every 5 seconds
 without blocking the main loop.

*/

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

// Update these with values suitable for your hardware/network.
byte mac[]    = {  0xDE, 0xED, 0xBA, 0xFE, 0xFE, 0xED };
IPAddress ip(172, 16, 0, 100);
IPAddress server(172, 16, 0, 2);

void callback(char* topic, byte* payload, unsigned int length) {
  // handle message arrived
}

EthernetClient ethClient;
PubSubClient client(ethClient);

long lastReconnectAttempt = 0;

boolean reconnect() {
  if (client.connect("arduinoClient")) {
    // Once connected, publish an announcement...
    client.publish("outTopic","hello world");
    // ... and resubscribe
    client.subscribe("inTopic");
  }
  return client.connected();
}

void setup()
{
  client.setServer(server, 1883);
  client.setCallback(callback);

  Ethernet.begin(mac, ip);
  delay(1500);
  lastReconnectAttempt = 0;
}


void loop()
{
  if (!client.connected()) {
    long now = millis();
    if (now - lastReconnectAttempt > 5000) {
      lastReconnectAttempt = now;
      // Attempt to reconnect
      if (reconnect()) {
        lastReconnectAttempt = 0;
      }
    }
  } else {
    // Client connected

    client.loop();
  }

}

@electrik
tried it but also no luck

C:\Users\p.\Documents\Arduino\GatewayW5x00MQTTClient\GatewayW5x00MQTTClient.ino: In function 'void setup()':
C:\Users\p.\Documents\Arduino\GatewayW5x00MQTTClient\GatewayW5x00MQTTClient.ino:213:10: error: 'class PubSubClient' has no member named 'setSocketTimeout'
   client.setSocketTimeout(1);
          ^~~~~~~~~~~~~~~~

exit status 1

Compilation error: 'class PubSubClient' has no member named 'setSocketTimeout'```

@electrik I've put the

#define MQTT_SOCKET_TIMEOUT 1

in the beginning where all other #defined constants are and it does not seeams to take this config.
I tried to use

setSocketTimeout(1)

but I can't seems to get the sketch to work with <PubSubClient.h>
I've added

EthernetClient ethClient;
PubSubClient client(ethClient);
client.setSocketTimeout(1);

but getting following error.

GatewayW5x00MQTTClient.ino:172:1: error: 'client' does not name a type
 client.setSocketTimeout(1);
 ^~~~~~

exit status 1

Compilation error: 'client' does not name a type

any ideas?

@electrik
Have you tested this in your enviroment/sketch?
Did it increase availability for your sketch?
If yes what was the single loop time before and after changing this?
I did test is on my example and it does not increase the availability for the main loop for my sketch, also you can see the printout from the serial monitor, the loop is run in the same 3s intervals like before, so maybe I am doing something wrong?

@electrik thank you for your suggestion, but are you talking about MQTT_SOCKET_TIMEOUT ?
If yes I did set this to 1s

#define MQTT_SOCKET_TIMEOUT 1

and did not change a thing

21:32:05.081 -> Loop count = 153
21:32:05.081 -> 471258 GWT:TPC:IP=192.168.11.111
21:32:06.098 -> 472262 GWT:RMQ:CONNECTING...
21:32:08.071 -> 474266 !GWT:RMQ:FAIL
21:32:08.071 -> Loop count = 154

If not please do let me know what you had in mind so I can check it out.

@OldSurferDude thanks for confirming that I have not missed anything when doing a resarch on this matter, if there will be no new suggestions I think I might have to post it to Development as dont see anyone suggesting any good workaround or a solution.

Hi @Guillermo-Schimmel,
I know it's closed but just noticed this issue, you most probably had STP (Spanning Tree Protocol) enabled on that port, which is normal for ent switch, and while it waits for a loop it blocks trafic from that port.
Disabling that feature should solve this problem.

Hello,
I'm new here so sorry if this is not the right place for this question.
But I am trying to build Arduino MQTT GW to act as a relay/light controller and report/interact with HomeAssistant.
I think I have worked out most of my problems and got it running as I wanted to, but I was testing failover senarios as the controller should be able to work independently of any other device as long it has power.
My config is kind of simple Arduino Mega with W5500 Ethernet module configured as MQTT GW
And the problem is that when network or HA/MQTT broker is unavailable when Arduino is restarted/booting it tries to reconnect to MQTT broker constantly and interupts the main loop everytime for around 3s which makes board basically unresponsive.

00:45:07.094 -> 549536 !GWT:RMQ:FAIL
00:45:07.094 -> Loop count = 179
00:45:07.094 -> 549538 GWT:TPC:IP=192.168.11.111
00:45:08.107 -> 550542 GWT:RMQ:CONNECTING...
00:45:10.130 -> 552547 !GWT:RMQ:FAIL
00:45:10.130 -> Loop count = 180
00:45:10.130 -> 552550 GWT:TPC:IP=192.168.11.111

Any ideas how I could disable reconnect function if that happens for example after 3 attempts? So the controller can work normally even if there is no connection to MQTT broker?