ESP8266 deep sleep and MQTT

Question

I am working on a project were I am putting my board into deep sleep mode, and it wakes up with an interrupt from a sensor. When it wakes from deep sleep I would like to send a message to my MQTT broker. The wiring works, the interrupt works, however, the code does not.

When I use the posted code, everything looks fine in the console, I get all my print statements which would make me assume it is working. However, my MQTT broker does not show any messages. But, if I move "sendMQTTMessage()" to the loop function it works fine and the messages come through to my broker.

Any suggestions would be greatly appreciated

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

const char* ssid = "*";
const char* ss_pswd = "*";
const char* mqtt_server = "*";
WiFiClient EspClient;
PubSubClient client(EspClient);

void wifi_setup() {
  Serial.print("Connecting to: ");
  Serial.println(ssid);
  WiFi.begin(ssid, ss_pswd);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println(".");
  }
  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}
void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    String ClientId = "ESP8266";
    ClientId += String(random(0xffff), HEX);
    if (client.connect(ClientId.c_str())) {
      Serial.println("connected");
      client.publish("outtopic", "hello world, finally");
      client.subscribe("/room/test");
    } else {
      Serial.print("failed, rc=");
      Serial.println(client.state());
      Serial.println("Try again...");
      delay(5000);
    }
  }
}
void sendMQTTMessage() {
  Serial.println("sending your message");
  if (!client.connected()) {
    reconnect();
  }
  client.publish("belmont/sensor/pir/hallway", "on");
}
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived: ");
  Serial.println(topic);
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
}
void setup() {
  Serial.begin(115200);
  wifi_setup();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
  sendMQTTMessage();
  Serial.println("going into deep sleep");
  ESP.deepSleep(10 * 1000000);
}

void loop() {
//  sendMQTTMessage();
//  delay(5000);
}

Answer 1

The answer for this actually goes to Juraj. It was the fact that I was missing a delay. In hindsight it makes sense, as even though I am competing tasks in order, the system is shutting down, before the actual message is sent. I added a delay(1000) between the "sendMQTTMessage()" and "ESP.deepsleep()" and it worked.