I put the below code on a Sonoff switch (which has an ESP8266 on it). I installed mosquitto as MQTT broker on my orange pi and tested it, so the broker is ok.

Now, when I subscribe to the topic I set, nothing is shown when my relay state changes:

mosquitto_sub -h localhost -t Sonoff-Out

I am sure I am just missing some configuration or a command...Any ideas?

main.h

#define PIN_PIR_SENSOR 14
#define PIN_RELAY  12
#define PIN_LED 13
#define RELAY_ON 1
#define RELAY_OFF 0
#define LED_ON 0
#define LED_OFF 1

#define CHILD_ID 73

// Enable debug prints to serial monitor
#define MY_DEBUG

// Use a bit lower baudrate for serial prints on ESP8266 than default in MyConfig.h
#define MY_BAUD_RATE 115200

#define MY_GATEWAY_MQTT_CLIENT
#define MY_GATEWAY_ESP8266

#define MY_ESP8266_SSID "REMOVED"
#define MY_ESP8266_PASSWORD "REMOVED"
#define MY_ESP8266_HOSTNAME "Sonoff-PIRSwitch-Lamp"

//#define MY_IP_ADDRESS 1,1,1,80
//#define MY_IP_GATEWAY_ADDRESS 1,1,1,10
//#define MY_IP_SUBNET_ADDRESS 255,255,255,0

//#define MY_USE_UDP
#define MY_CONTROLLER_IP_ADDRESS 1,1,1,1

// The port to keep open on node server mode
#define MY_PORT 1883

// How many clients should be able to connect to this gateway (default 1)
//#define MY_GATEWAY_MAX_CLIENTS 1

// Set this node's subscribe and publish topic prefix
#define MY_MQTT_PUBLISH_TOPIC_PREFIX "Sonoff-Out"
#define MY_MQTT_SUBSCRIBE_TOPIC_PREFIX "Sonoff-In"

// Set MQTT client id
#define MY_MQTT_CLIENT_ID "Sonoff-PIRSwitch-Lamp"

#if defined(MY_USE_UDP)
#include <WiFiUdp.h>
#endif

#include <Arduino.h>
//#include <ESP8266mDNS.h>
#include <ESP8266WiFi.h>
#include <MySensors.h>

void setup();
void loop();
void present();
void receive(const MyMessage &message);
void ISR_PIRPinHasChanged();
void SetRelayAndLedStatus();
void ToggleRelay();
void TransmitStatusToController();

main.cpp

#include "main.h"

int currentRelayStatus;
MyMessage msg(CHILD_ID,V_STATUS);

void setup(){
  pinMode(PIN_LED, OUTPUT);
  pinMode(PIN_RELAY, OUTPUT);
  pinMode(PIN_PIR_SENSOR, INPUT);

  currentRelayStatus = RELAY_OFF;
  attachInterrupt(PIN_PIR_SENSOR, ISR_PIRPinHasChanged, RISING);

  //flash led
  digitalWrite(PIN_LED,LED_ON);
  delay(100);
  digitalWrite(PIN_LED,LED_OFF);
  delay(100);
  digitalWrite(PIN_LED,LED_OFF);
  delay(100);
  digitalWrite(PIN_LED,LED_OFF);
  delay(100);
}

void loop()
{

}

void presentation()  {
  // Send the sketch version information
  sendSketchInfo("Sonoff PIR Switch", "1.1");
  // Register sensor
  present(CHILD_ID, S_BINARY);
  SetRelayAndLedStatus();
  TransmitStatusToController();
}

void receive(const MyMessage &message)
{
  if (message.type==V_STATUS  && message.sensor==CHILD_ID) {
    if(message.getBool() == true)
    {
      currentRelayStatus = RELAY_ON;
    }
    else{
      currentRelayStatus = RELAY_OFF;
    }
    SetRelayAndLedStatus();
    TransmitStatusToController();
  }
}


void ISR_PIRPinHasChanged(){
  int currentPinStatus = digitalRead(PIN_PIR_SENSOR);
  if(currentPinStatus == LOW){
    Serial.println("ISR fired, pin LOW");
  }
  else{
    Serial.println("ISR fired, pin HIGH");
    ToggleRelay();
  }
}

void ToggleRelay(){
  if(currentRelayStatus == RELAY_ON){
    Serial.println("toggling relay to OFF");
    currentRelayStatus = RELAY_OFF;
  }
  else{
    Serial.println("toggling relay to ON");
    currentRelayStatus = RELAY_ON;
  }
  SetRelayAndLedStatus();
  TransmitStatusToController();
}

void SetRelayAndLedStatus(){
  if(currentRelayStatus == RELAY_ON){
    Serial.println("switching on");
    digitalWrite(PIN_LED, LED_ON);
    digitalWrite(PIN_RELAY, RELAY_ON);
  }
  else{
    Serial.println("switching off");
    digitalWrite(PIN_LED, LED_OFF);
    digitalWrite(PIN_RELAY, RELAY_OFF);
  }
}

void TransmitStatusToController(){
  Serial.println("sending status to controller");
  if(currentRelayStatus == RELAY_ON){
    send(msg.set(true));
  }
  else{
    send(msg.set(false));
  }
}