gateway:

mysgw: Starting gateway...
mysgw: Protocol version - 2.2.0-beta
mysgw: MCO:BGN:INIT GW,CP=RNNG----,VER=2.2.0-beta
mysgw: TSF:LRT:OK
mysgw: TSM:INIT
mysgw: TSF:WUR:MS=0
mysgw: TSM:INIT:TSP OK
mysgw: TSM:INIT:GW MODE
mysgw: TSM:READY:ID=0,PAR=0,DIS=0
mysgw: MCO:REG:NOT NEEDED
mysgw: MCO:BGN:STP
mysgw: MCO:BGN:INIT OK,TSP=1
mysgw: Attempting MQTT connection...
mysgw: connected to 127.0.0.1
mysgw: MQTT connected
mysgw: Sending message on topic: mysensors-out/0/255/0/0/18

skatch:

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * REVISION HISTORY
 * Version 1.0 - Henrik EKblad
 *
 * DESCRIPTION
 * Example sketch showing how to measue light level using a LM393 photo-resistor
 * http://www.mysensors.org/build/light
 */

// Enable debug prints to serial monitor
#define MY_DEBUG
#define MY_NODE_ID 66

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

#define MY_MQTT_TOPIC_PREFIX "mygateway"

#include <MySensors.h>

#define CHILD_ID_LIGHT 15
#define LIGHT_SENSOR_ANALOG_PIN 0

unsigned long SLEEP_TIME = 30000; // Sleep time between reads (in milliseconds)

MyMessage msg(CHILD_ID_LIGHT, V_LIGHT_LEVEL);
int lastLightLevel;


void presentation()
{
    // Send the sketch version information to the gateway and Controller
    sendSketchInfo("Light Sensor", "1.0");

    // Register all sensors to gateway (they will be created as child devices)
    present(CHILD_ID_LIGHT, S_LIGHT_LEVEL);
}

void loop()
{
    int16_t lightLevel = (1023-analogRead(LIGHT_SENSOR_ANALOG_PIN))/10.23;
    Serial.println(lightLevel);
    if (lightLevel != lastLightLevel) {
        send(msg.set(lightLevel));
        lastLightLevel = lightLevel;
    }
    sleep(SLEEP_TIME);
}