Arduino/ESP32 can't connect to to MQTT broker - c++

Question

I'm working on getting my ESP32 board (also Arduino R3 & Nano) to connect to a HiveMQ broker, but it will not connect. I've tried various ports, different brokers, disabling ad blocking on my network, etc., but nothing seems to make a difference.
#include <Arduino.h>
#include <ArduinoJson.h>
#include <WiFi.h>
#include <PubSubClient.h>
void MQTT_callback(char* topic, byte* message, unsigned int length);
void setup() {
Serial.begin(115200);
while (!Serial);
delay(250);
Serial.println("setup beginning");
Serial.print("Connecting to WiFi...");
WiFi.begin("...", "...");
for (int i=0; i<30 && WiFi.status() != WL_CONNECTED; ++i) {
Serial.print(".");
delay(250);
}
if (WiFi.status() != WL_CONNECTED) {
Serial.println(" failed");
Serial.println("Oh no, no Wifi!? You're back in 1980! That's horrible...");
return;
} else {
Serial.println(" connected!");
}
WiFiClient espClient;
PubSubClient client(espClient);
const char* MQTT_URL = "somereallylongstring.s2.eu.hivemq.cloud";
const int MQTT_PORT = 8883;
const char* MQTT_uid = "...";
const char* MQTT_pwd = "...";
const String MQTT_client = "esp32-client-" + WiFi.macAddress();
client.setServer(MQTT_URL, MQTT_PORT);
client.setCallback(MQTT_callback);
if (!client.connected()) {
Serial.println("Connecting to MQTT broker with client '" + MQTT_client + "'...");
for (int i=0; i<10 && !client.connected(); ++i) {
if (client.connect(MQTT_client.c_str(), MQTT_uid, MQTT_pwd)) {
Serial.println("Connected to MQTT broker");
} else {
Serial.print("Connection to MQTT broker failed: ");
#define C(x) case (x): Serial.println(#x); break;
switch (client.state()) {
C(MQTT_CONNECTION_TIMEOUT)
C(MQTT_CONNECTION_LOST)
C(MQTT_CONNECT_FAILED)
C(MQTT_DISCONNECTED)
C(MQTT_CONNECTED)
C(MQTT_CONNECT_BAD_PROTOCOL)
C(MQTT_CONNECT_BAD_CLIENT_ID)
C(MQTT_CONNECT_UNAVAILABLE)
C(MQTT_CONNECT_BAD_CREDENTIALS)
C(MQTT_CONNECT_UNAUTHORIZED)
}
#undef C
}
}
}
if (client.connected()) {
const char* topic = "/sensors/sean/salt_tank";
StaticJsonDocument<MQTT_MAX_PACKET_SIZE> doc;
doc["ts"] = "2023-01-15 20:24:00";
doc["temp"] = 82.1;
doc["tds"] = 821;
doc["ph"] = 7.6;
String output;
serializeJson(doc, output);
Serial.println("Publishing message to " + String(topic) + output);
client.publish(topic, output.c_str());
}
Serial.println("setup complete!");
}
void loop() {
}
void MQTT_callback(char* topic, byte* message, unsigned int length) {
String msg = "";
for (int i=0; i<length; ++i)
msg += (char)message[i];
Serial.println("Message arrived on topic " + String(topic) + ":");
Serial.println(msg);
}
Here's the output:
22:11:00.629 > setup beginning
22:11:00.631 > Connecting to WiFi........ connected!
22:11:02.001 > Connecting to MQTT broker with client 'esp32-client-08:3A:F2:B8:8B:CC'...
22:11:17.512 > Connection to MQTT broker failed: MQTT_CONNECTION_TIMEOUT
22:11:32.670 > Connection to MQTT broker failed: MQTT_CONNECTION_TIMEOUT
I don't know if this makes a difference, but I'm using an ARM MacBook. I don't know if the difference in libraries could be causing an issue or not. Thanks!