A simple client for MQTT. More...

#include <Arduino.h>
#include "Client.h"
#include "IPAddress.h"
#include "Stream.h"

Classes
class	PubSubClient
	This class provides a client for doing simple publish and subscribe messaging with a server that supports MQTT. More...

Macros
#define	MQTT_VERSION_3_1 3
	Defines MQTT 3.1 protocol version, see MQTT_VERSION.

#define	MQTT_VERSION_3_1_1 4
	Defines MQTT 3.1.1 protocol version, see MQTT_VERSION.

#define	MQTT_VERSION MQTT_VERSION_3_1_1
	Sets the version of the MQTT protocol to use (3.1 or 3.1.1). [MQTT_VERSION_3_1, MQTT_VERSION_3_1_1].

#define	MQTT_MAX_POSSIBLE_PACKET_SIZE 268435455
	Maximum packet size defined by MQTT protocol.

#define	MQTT_MAX_PACKET_SIZE 256
	Sets the largest packet size, in bytes, the client will handle. Any packet received that exceeds this size will be ignored. This value can be overridden by calling setBufferSize.

#define	MQTT_KEEPALIVE 15
	Sets the keepalive interval, in seconds, the client will use. This is used to maintain the connection when no other packets are being sent or received. This value can be overridden by calling setKeepAlive.

#define	MQTT_SOCKET_TIMEOUT 15
	Sets the timeout, in seconds, when reading from the network. This also applies as the timeout for calls to connect. This value can be overridden by calling setSocketTimeout.

#define	MQTT_MAX_TRANSFER_SIZE 80
	Sets the maximum number of bytes passed to the network client in each write call. Some hardware has a limit to how much data can be passed to them in one go, such as the Arduino Wifi Shield e.g. use 80.

#define	MQTT_CONNECTION_TIMEOUT -4
	The network connection timed out or server didn't respond within the keepalive time.

#define	MQTT_CONNECTION_LOST -3
	The network connection was lost/broken.

#define	MQTT_CONNECT_FAILED -2
	The network connection failed.

#define	MQTT_DISCONNECTED -1
	The client is disconnected cleanly.

#define	MQTT_CONNECTED 0
	The client is connected.

#define	MQTT_CONNECT_BAD_PROTOCOL 1
	The server does not support the requested MQTT version.

#define	MQTT_CONNECT_BAD_CLIENT_ID 2
	The server rejected the client identifier.

#define	MQTT_CONNECT_UNAVAILABLE 3
	The server was unable to accept the connection.

#define	MQTT_CONNECT_BAD_CREDENTIALS 4
	The username or password is not valid.

#define	MQTT_CONNECT_UNAUTHORIZED 5
	The client is not authorized to connect to the server.

#define	MQTT_QOS0 ((uint8_t)0)
	Quality of Service 0: At most once.

#define	MQTT_QOS1 ((uint8_t)1)
	Quality of Service 1: At least once.

#define	MQTT_QOS2 ((uint8_t)2)

#define	MQTT_CALLBACK_SIGNATURE void (callback)(char topic, uint8_t* payload, size_t plength)

Detailed Description

A simple client for MQTT.

Author: Nicholas O'Leary - http://knolleary.net; Holger Mueller - https://github.com/hmueller01/pubsubclient3

Copyright: MIT License 2008-2025

This file is part of the PubSubClient library.

Definition in file PubSubClient.h.

Macro Definition Documentation

◆ MQTT_CALLBACK_SIGNATURE

#define MQTT_CALLBACK_SIGNATURE void (*callback)(char* topic, uint8_t* payload, size_t plength)

Define the signature required by any callback function.

Parameters

topic	The topic of the message.
payload	The payload of the message.
plength	The length of the payload.

Definition at line 146 of file PubSubClient.h.

◆ MQTT_KEEPALIVE

#define MQTT_KEEPALIVE 15

Sets the keepalive interval, in seconds, the client will use. This is used to maintain the connection when no other packets are being sent or received. This value can be overridden by calling setKeepAlive.

Note: Default value is 15 seconds.

Definition at line 57 of file PubSubClient.h.

◆ MQTT_MAX_PACKET_SIZE

#define MQTT_MAX_PACKET_SIZE 256

Sets the largest packet size, in bytes, the client will handle. Any packet received that exceeds this size will be ignored. This value can be overridden by calling setBufferSize.

Note: Default value is 256 bytes.

Definition at line 47 of file PubSubClient.h.

◆ MQTT_MAX_POSSIBLE_PACKET_SIZE

#define MQTT_MAX_POSSIBLE_PACKET_SIZE 268435455

Maximum packet size defined by MQTT protocol.

Definition at line 37 of file PubSubClient.h.

◆ MQTT_MAX_TRANSFER_SIZE

#define MQTT_MAX_TRANSFER_SIZE 80

Sets the maximum number of bytes passed to the network client in each write call. Some hardware has a limit to how much data can be passed to them in one go, such as the Arduino Wifi Shield e.g. use 80.

Note: Defaults to undefined, which passes the entire packet in each write call.

Definition at line 77 of file PubSubClient.h.

◆ MQTT_SOCKET_TIMEOUT

#define MQTT_SOCKET_TIMEOUT 15

Sets the timeout, in seconds, when reading from the network. This also applies as the timeout for calls to connect. This value can be overridden by calling setSocketTimeout.

Note: Default value is 15 seconds.

Definition at line 67 of file PubSubClient.h.

◆ MQTT_VERSION

#define MQTT_VERSION MQTT_VERSION_3_1_1

Sets the version of the MQTT protocol to use (3.1 or 3.1.1). [MQTT_VERSION_3_1, MQTT_VERSION_3_1_1].

Note: Default value is MQTT_VERSION_3_1_1 for MQTT 3.1.1.

Definition at line 30 of file PubSubClient.h.

◆ MQTT_VERSION_3_1

#define MQTT_VERSION_3_1 3

Defines MQTT 3.1 protocol version, see MQTT_VERSION.

Definition at line 20 of file PubSubClient.h.

◆ MQTT_VERSION_3_1_1

#define MQTT_VERSION_3_1_1 4

Defines MQTT 3.1.1 protocol version, see MQTT_VERSION.

Definition at line 21 of file PubSubClient.h.

Classes

Macros