Problem with connecting to a MQTT Server

Projects General Guidance
1

I'm currently trying to communicate with my ESP32 via a MQTT Server. The issue is that the code I have only sometimes works and I don't know why. My PC is connecting just fine using Node Red.
The example code from the Library works, so it shouldn't be a hardware issue.

// This example uses an ESP32 Development Board
// to connect to shiftr.io.
//
// You can check on your device after a successful
// connection here: https://www.shiftr.io/try.
//
// by Joël Gähwiler
// https://github.com/256dpi/arduino-mqtt

#include <WiFi.h>
#include <MQTT.h>

const char ssid[] = "HTLW3R-2.5"; //Just my school WIFI
const char pass[] = "HTLW3R-2.5";

WiFiClient net;
MQTTClient client;

unsigned long lastMillis = 0;

IPAddress Raspi(10, 18, 2, 120); //IP of my Raspberry PI

void connect() {
  Serial.print("checking wifi...");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print(".");
    delay(1000);
  }


  Serial.print("\nconnecting...");
  while (!client.connect("")) {
    Serial.print(".");              //Can't connect and gets stuck here
    delay(1000);
  }

  Serial.println("\nconnected!");

  client.subscribe("testSky");
  // client.unsubscribe("/hello");
}

void messageReceived(String &topic, String &payload) {
  Serial.println("incoming: " + topic + " - " + payload);

  // Note: Do not use the client in the callback to publish, subscribe or
  // unsubscribe as it may cause deadlocks when other things arrive while
  // sending and receiving acknowledgments. Instead, change a global variable,
  // or push to a queue and handle it in the loop after calling `client.loop()`.
}

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, pass);

  // Note: Local domain names (e.g. "Computer.local" on OSX) are not supported
  // by Arduino. You need to set the IP address directly.
  client.begin(Raspi, 1883, net); //Two Options available: (IP, Network) or (IP, Port, Network) 1. Option seems to function better but far from consistent
  client.onMessage(messageReceived);

  connect();
}

void loop() {
  client.loop();
  delay(10);  // <- fixes some issues with WiFi stability

  if (!client.connected()) {
    connect();
  }

  // publish a message roughly every second.
  if (millis() - lastMillis > 1000) {
    lastMillis = millis();
    client.publish("testSky", "world1");    //This should just send itself a message. My PC is also listening for this topic
  }
}

I'm currently using Mosquitto as my server. The Settings are:
allow_anonymous true
listener 1883

2

Welcome to the forum

I am not familiar with the MQTT library that you are using as I normally use the PubSubClient. Where did you get the library from ?

3

it's in the comment at the top of the code

4

Thank you

5

What do you mean by this ?

Please describe what happens when you upload the sketch. Is a connection established with the MQTT server, does the problem occur with any/all MQTT servers or only yours ?

6

Turns out the School Wifi is just set up to block certain connections, and that blocking fails sometimes.

7

Thank you for reporting back the cause of the problem

Good luck with your project

8

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