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Home » Eclipse Projects » Mosquitto » ESP8266 not able to connect local mosquitto broker(ESP8266 can connect and other mqtt broker without any problem. But not able to connect local Mosquitto broker)
ESP8266 not able to connect local mosquitto broker [message #1830640] Thu, 30 July 2020 10:14
Cyno Sure is currently offline Cyno SureFriend
Messages: 1
Registered: July 2020
Junior Member
I can connect ESP8266 to Pub/Sub all works.

But while using the same ESP8266 to connect my local mosquitto broker, it just does not establish connection with the local broker. (I actually tried several local mosquito brokers and none of them works.)

At first I thought it was my local broker that has problem. However, when using MQTT.fx and mosquitto_pub/sub tools, everything works just fine.

It seems the only device that does not work with my local broker is the ESP8266. :-(

Here is my code. Can someone please help? Thanks a lot! (BTW. the code is also attached in this post.)

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

// ATTENTION:The following line works as 
// this is's ip
//IPAddress mqtt_server (5, 196, 95, 208);

// ATTENTION: This DONT work as this is 
// my local broker's ip
IPAddress mqtt_server (192, 168, 0, 104); 

WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE	(50)
char msg[MSG_BUFFER_SIZE];
int value = 0;

const char* ssid = "taichi-maker";
const char* password = "12345678";

void setup_wifi() {

  // We start by connecting to a WiFi network
  Serial.print("Connecting to ");

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {


  Serial.println("WiFi connected");
  Serial.println("IP address: ");

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print("] ");
  for (int i = 0; i < length; i++) {

  // Switch on the LED if an 1 was received as first character
  if ((char)payload[0] == '1') {
    digitalWrite(BUILTIN_LED, LOW);   // Turn the LED on (Note that LOW is the voltage level
    // but actually the LED is on; this is because
    // it is active low on the ESP-01)
  } else {
    digitalWrite(BUILTIN_LED, HIGH);  // Turn the LED off by making the voltage HIGH


void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Create a random client ID
    String clientId = "ESP8266Client-";
    clientId += String(random(0xffff), HEX);
    // Attempt to connect
    if (client.connect(clientId.c_str())) {
      // Once connected, publish an announcement...
      client.publish("outTopic", "hello world");
      // ... and resubscribe
    } else {
      Serial.print("failed, rc=");
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying

void setup() {
  pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
  client.setServer(mqtt_server, 1883);

void loop() {

  if (!client.connected()) {

  unsigned long now = millis();
  if (now - lastMsg > 2000) {
    lastMsg = now;
    snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);
    Serial.print("Publish message: ");
    client.publish("outTopic", msg);

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