MJS code of a start procedure in Mongoose-OS with a pattern which will wait until WiFi, MQTT and SNTP connections are succefully set up.

system_start.js

load('api_http.js');
load('api_config.js');

let connected = 0;
let step = 3;
let started = false;
let watchDog = 0;

let timeOut = 30; // might be defined in the configuration ...

let events = {

	_netEventHandler: function(ev, evdata, ctx) {
		connected |= 0x01;
		Timer.del(watchDog);
		watchDog = Timer.set(1000 * timeOut, 0, start, {hasConnections: false});
		Log.info('Connected to WiFi ... state: ' + JSON.stringify(connected));
		if (connected === 0x07) {
			Timer.del(watchDog);
			start({hasConnections: true});
		}
	},

	_mqttEventHandler: function(conn, ev, data, ctx) {
		if (ev === MQTT.EV_CONNACK) {
			connected |= 0x02;
			Timer.del(watchDog);
			watchDog = Timer.set(1000 * timeOut, 0, start,  {hasConnections: false});
			Log.info('Connected to MQTT ... state: ' + JSON.stringify(connected));
			if (connected === 0x07) {
				Timer.del(watchDog);
				start({hasConnections: true});
			}
		}
	},

	_sntpEventHandler: function(ev, evdata, ctx) {
		if (ev === Event.SYS + 3) {
			connected |= 0x04;
			Timer.del(watchDog);
			watchDog = Timer.set(1000 * timeOut, 0, start,  {hasConnections: false});
			Log.info('Time set via SNTP ... state: ' + JSON.stringify(connected) + " - connected: " + JSON.stringify(connected));
			if (connected === 0x07) {
				Timer.del(watchDog);
				start({hasConnections: true});
			}
		}
	}

};

function prepareConnections(ctx) {
	watchDog = Timer.set(1000 * timeOut, 0, start, {hasConnections: false});
	// Monitor network connectivity.
	Event.addHandler(Net.STATUS_GOT_IP, events._netEventHandler, ctx),
	// Monitor MQTT connectivity.
	MQTT.setEventHandler(events._mqttEventHandler, ctx);
	// Monitor SNTP changes
	Event.addGroupHandler(Event.SYS, events._sntpEventHandler, ctx);
}

function start(sysInfo) {
	
	// start only once
	if (started) {
		return;
	}

  // if the watch dog timer started the system, we will fallback in the "old habit"
	connected = (sysInfo !== null && sysInfo.hasConnections) ? connected : 0;
  if (connected === 0) {
		Log.info('Started without connection by watch dog timer ...');
  }

	started = true;
	Log.info('Start module ...');

	// ***********************************
	// Put your own starting code here ...
	// ***********************************
}

This tool will establish configured WiFi, MQTT and SNTP connections, guarded by a watchdog. When all connections are active, the function "start" will be called, from there the system start may continue. If a timeout occurs, the start will be continued withtout the established connections.

To use, just add this MJS file in your Mongoose-OS "fs" directory, and in "fs/init.js" add the call "load('system_start.js');" on top of the file. Then, also in "fs/init.js" ad the call "prepareConnections(this);" - and in the routine "function start(sysInfo) " add your own starting code for your app. That's it ...