Uncaught Error: This socket is closed. MQTT connectivity issues

@Gordon

That's interesting - what happens if you switch back to the original
MQTT?

I executed reset(true) changed the mqtt require to mqtt = require("MQTT").connect then uploaded my code.
after about 3 mqtt messages I get: MQTT disconnected... reconnecting. Then mqtt reconnects with message MQTT connected

You could try replacing:

I changed the code with your suggestion, executed reset(true) then uploaded the code.
After about 3 messages I receive: MQTT disconnected... reconnecting. Then mqtt reconnects with message MQTT connected

code:

var MQTT_HOST = "192.168.0.17";
var PATH = "/mydevice/";
var mqtt;
var eth;

var inProcess =  false;
var shortPress = 1000; // ms 1 sec
var longPress = 5000; // ms 5 secs
var pressPin = B3;

// output like 'open collector' see reference
pinMode(pressPin,"opendrain"); 
pressPin.set();

function mqttMessage(pub) {
  console.log(
     "MQTT=> ",pub.topic,pub.message);
  if (pub.topic==PATH+"computer") {
    if (pub.message == "shutdown") {
      press(shortPress);
    }
  }
}

function mqttConnect() {
  console.log("mqttConnect");
  mqtt = require("MQTT").connect({
    host: MQTT_HOST,
  });
  mqtt.on('connected', function() {
    console.log("MQTT connected");
    // subscribe to wildcard for our name
    mqtt.subscribe(PATH+"#");
  });
  mqtt.on('publish', mqttMessage);
  var thisMQTT = mqtt;
  mqtt.on('disconnected', function() {
    if (mqtt!=thisMQTT) {
      console.log("MQTT disconnected - but we already have a new MQTT");
      return;
    }
    console.log("MQTT disconnected... reconnecting.");
    setTimeout(function() {
      mqtt.connect();
    }, 1000);
  });
}

function press(short) {
  // ignore press function when one is still going on
  if (inProcess) return; 
  inProcess = true;
  // Relays (board) act in an inverse manner
  // reset() will latch the relay
  pressPin.reset();
  setTimeout(function(){
      // Relays (board) act in an inverse manner
      // set() will unlatch the relay
      pressPin.set();
      inProcess = false;
    },(short) ? shortPress : longPress);
}

setWatch(function(e) {
  digitalWrite(LED1, e.state);
  press(shortPress);
}, BTN, { repeat: true });

function onInit() {
  console.log("Connecting to Ethernet");

  SPI2.setup({ mosi:B15, miso:B14, sck:B13 });
  eth = require("WIZnet").connect(SPI2, B10);

  isConnected = eth.setIP();

  if (isConnected == true) {
    mqttConnect();
  }
}

Is it good practice to execute reset(true) before I upload any new code in the future?