ESP-MQTT
概述
ESP-MQTT 是 MQTT 协议客户端的实现,MQTT 是一种基于发布/订阅模式的轻量级消息传输协议。ESP-MQTT 当前支持 MQTT v5.0。
特性
支持基于 TCP 的 MQTT、基于 Mbed TLS 的 SSL、基于 WebSocket 的 MQTT 以及基于 WebSocket Secure 的 MQTT
通过 URI 简化配置流程
多个实例(一个应用程序中有多个客户端)
支持订阅、发布、认证、遗嘱消息、保持连接心跳机制以及 3 个服务质量 (QoS) 级别(组成全功能客户端)
应用示例
protocols/mqtt/tcp:基于 TCP 的 MQTT,默认端口 1883
protocols/mqtt/ssl:基于 TLS 的 MQTT,默认端口 8883
protocols/mqtt/ssl_ds:基于 TLS 的 MQTT,使用数字签名外设进行身份验证,默认端口 8883
protocols/mqtt/ssl_mutual_auth:基于 TLS 的 MQTT,使用证书进行身份验证,默认端口 8883
protocols/mqtt/ssl_psk:基于 TLS 的 MQTT,使用预共享密钥进行身份验证,默认端口 8883
protocols/mqtt/ws:基于 WebSocket 的 MQTT,默认端口 80
protocols/mqtt/wss:基于 WebSocket Secure 的 MQTT,默认端口 443
protocols/mqtt5: 使用 ESP-MQTT 库连接 MQTT v5.0 的服务器
MQTT 消息重传
调用 esp_mqtt_client_publish
或其非阻塞形式 esp_mqtt_client_enqueue
,可以创建新的 MQTT 消息。
QoS 0 的消息将只发送一次,QoS 1 和 2 具有不同行为,因为协议需要执行额外步骤来完成该过程。
ESP-MQTT 库将始终重新传输未确认的 QoS 1 和 2 发布消息,以避免连接错误导致信息丢失,虽然 MQTT 规范要求仅在重新连接且 Clean Session 标志设置为 0 时重新传输(针对此行为,将 disable_clean_session
设置为 true)。
可能需要重传的 QoS 1 和 2 消息总是处于排队状态,但若使用 esp_mqtt_client_publish
则会立即进行第一次传输尝试。未确认消息的重传将在 message_retransmit_timeout
之后进行。在 CONFIG_MQTT_OUTBOX_EXPIRED_TIMEOUT_MS 之后,消息会过期并被删除。如已设置 CONFIG_MQTT_REPORT_DELETED_MESSAGES,则会发送事件来通知用户。
配置
通过设置 esp_mqtt_client_config_t
结构体中的字段来进行配置。配置结构体包含以下子结构体,用于配置客户端的多种操作。
esp_mqtt_client_config_t::broker_t
- 允许设置地址和安全验证。
esp_mqtt_client_config_t::credentials_t
- 用于身份验证的客户端凭据。
esp_mqtt_client_config_t::session_t
- MQTT 会话相关配置。
esp_mqtt_client_config_t::network_t
- 网络相关配置。
esp_mqtt_client_config_t::task_t
- 允许配置 FreeRTOS 任务。
esp_mqtt_client_config_t::buffer_t
- 输入输出的缓冲区大小。
下文将详细介绍不同配置。
服务器
地址
通过 address
结构体的 uri
字段或者 hostname
、transport
以及 port
的组合,可以设置服务器地址。也可以选择设置 path
,该字段对 WebSocket 连接而言非常有用。
使用 uri
字段的格式为 scheme://hostname:port/path
。
当前支持
mqtt
、mqtts
、ws
和wss
协议基于 TCP 的 MQTT 示例:
mqtt://mqtt.eclipseprojects.io
:基于 TCP 的 MQTT,默认端口 1883mqtt://mqtt.eclipseprojects.io:1884
:基于 TCP 的 MQTT,端口 1884mqtt://username:password@mqtt.eclipseprojects.io:1884
:基于 TCP 的 MQTT, 端口 1884,带有用户名和密码
基于 SSL 的 MQTT 示例:
mqtts://mqtt.eclipseprojects.io
:基于 SSL 的 MQTT,端口 8883mqtts://mqtt.eclipseprojects.io:8884
:基于 SSL 的 MQTT,端口 8884
基于 WebSocket 的 MQTT 示例:
ws://mqtt.eclipseprojects.io:80/mqtt
基于 WebSocket Secure 的 MQTT 示例:
wss://mqtt.eclipseprojects.io:443/mqtt
最简配置:
const esp_mqtt_client_config_t mqtt_cfg = {
.broker.address.uri = "mqtt://mqtt.eclipseprojects.io",
};
esp_mqtt_client_handle_t client = esp_mqtt_client_init(&mqtt_cfg);
esp_mqtt_client_register_event(client, ESP_EVENT_ANY_ID, mqtt_event_handler, client);
esp_mqtt_client_start(client);
备注
默认情况下,MQTT 客户端使用事件循环库来发布相关 MQTT 事件(已连接、已订阅、已发布等)。
验证
为验证服务器身份,对于使用 TLS 的安全链接,必须设置 verification
结构体。
服务器证书可设置为 PEM 或 DER 格式。如要选择 DER 格式,必须设置等效 certificate_len
字段,否则应在 certificate
字段传入以空字符结尾的 PEM 格式字符串。
- 从服务器获取证书,例如:
mqtt.eclipseprojects.io
openssl s_client -showcerts -connect mqtt.eclipseprojects.io:8883 < /dev/null \ 2> /dev/null | openssl x509 -outform PEM > mqtt_eclipse_org.pem
- 从服务器获取证书,例如:
检查示例应用程序:protocols/mqtt/ssl
配置:
const esp_mqtt_client_config_t mqtt_cfg = {
.broker = {
.address.uri = "mqtts://mqtt.eclipseprojects.io:8883",
.verification.certificate = (const char *)mqtt_eclipse_org_pem_start,
},
};
客户端凭据
credentials
字段下包含所有客户端相关凭据。
认证
可以通过 authentication
字段设置认证参数。客户端支持以下认证方式:
password
:使用密码
certificate
和key
:进行双向 TLS 身份验证,PEM 或 DER 格式均可
use_secure_element
:使用 ESP32-WROOM-32SE 中的安全元素
ds_data
:使用某些乐鑫设备的数字签名外设
会话
使用 session
字段进行 MQTT 会话相关配置。
遗嘱消息 (LWT)
通过设置 last_will
结构体的以下字段,MQTT 会在一个客户端意外断开连接时通过遗嘱消息通知其他客户端。
在项目配置菜单中设置 MQTT
通过 idf.py menuconfig
,可以在 Component config
> ESP-MQTT Configuration
中找到 MQTT 设置。
相关设置如下:
CONFIG_MQTT_PROTOCOL_311:启用 MQTT 协议 3.1.1 版本
CONFIG_MQTT_TRANSPORT_SSL 和 CONFIG_MQTT_TRANSPORT_WEBSOCKET:启用特定 MQTT 传输层,例如 SSL、WEBSOCKET 和 WEBSOCKET_SECURE
CONFIG_MQTT_CUSTOM_OUTBOX:禁用 mqtt_outbox 默认实现,因此可以提供特定实现
事件
MQTT 客户端可能会发布以下事件:
MQTT_EVENT_BEFORE_CONNECT
:客户端已初始化并即将开始连接至服务器。MQTT_EVENT_CONNECTED
:客户端已成功连接至服务器。客户端已准备好收发数据。MQTT_EVENT_DISCONNECTED
:由于无法读取或写入数据,例如因为服务器无法使用,客户端已终止连接。MQTT_EVENT_SUBSCRIBED
:服务器已确认客户端的订阅请求。事件数据将包含订阅消息的消息 ID。MQTT_EVENT_UNSUBSCRIBED
:服务器已确认客户端的退订请求。事件数据将包含退订消息的消息 ID。MQTT_EVENT_PUBLISHED
:服务器已确认客户端的发布消息。消息将仅针对 QoS 级别 1 和 2 发布,因为级别 0 不会进行确认。事件数据将包含发布消息的消息 ID。MQTT_EVENT_DATA
:客户端已收到发布消息。事件数据包含:消息 ID、发布消息所属主题名称、收到的数据及其长度。对于超出内部缓冲区的数据,将发布多个MQTT_EVENT_DATA
,并更新事件数据的current_data_offset
和total_data_len
以跟踪碎片化消息。MQTT_EVENT_ERROR
:客户端遇到错误。使用事件数据error_handle
字段中的error_type
,可以发现错误。错误类型决定error_handle
结构体的哪些部分会被填充。
API 参考
Header File
This header file can be included with:
#include "mqtt_client.h"
This header file is a part of the API provided by the
mqtt
component. To declare that your component depends onmqtt
, add the following to your CMakeLists.txt:REQUIRES mqtt
or
PRIV_REQUIRES mqtt
Functions
-
esp_mqtt_client_handle_t esp_mqtt_client_init(const esp_mqtt_client_config_t *config)
Creates MQTT client handle based on the configuration.
- 参数
config -- MQTT configuration structure
- 返回
mqtt_client_handle if successfully created, NULL on error
-
esp_err_t esp_mqtt_client_set_uri(esp_mqtt_client_handle_t client, const char *uri)
Sets MQTT connection URI. This API is usually used to overrides the URI configured in esp_mqtt_client_init.
- 参数
client -- MQTT client handle
uri --
- 返回
ESP_FAIL if URI parse error, ESP_OK on success
-
esp_err_t esp_mqtt_client_start(esp_mqtt_client_handle_t client)
Starts MQTT client with already created client handle.
- 参数
client -- MQTT client handle
- 返回
ESP_OK on success ESP_ERR_INVALID_ARG on wrong initialization ESP_FAIL on other error
-
esp_err_t esp_mqtt_client_reconnect(esp_mqtt_client_handle_t client)
This api is typically used to force reconnection upon a specific event.
- 参数
client -- MQTT client handle
- 返回
ESP_OK on success ESP_ERR_INVALID_ARG on wrong initialization ESP_FAIL if client is in invalid state
-
esp_err_t esp_mqtt_client_disconnect(esp_mqtt_client_handle_t client)
This api is typically used to force disconnection from the broker.
- 参数
client -- MQTT client handle
- 返回
ESP_OK on success ESP_ERR_INVALID_ARG on wrong initialization
-
esp_err_t esp_mqtt_client_stop(esp_mqtt_client_handle_t client)
Stops MQTT client tasks.
Notes:
Cannot be called from the MQTT event handler
- 参数
client -- MQTT client handle
- 返回
ESP_OK on success ESP_ERR_INVALID_ARG on wrong initialization ESP_FAIL if client is in invalid state
-
int esp_mqtt_client_subscribe_single(esp_mqtt_client_handle_t client, const char *topic, int qos)
Subscribe the client to defined topic with defined qos.
Notes:
Client must be connected to send subscribe message
This API is could be executed from a user task or from a MQTT event callback i.e. internal MQTT task (API is protected by internal mutex, so it might block if a longer data receive operation is in progress.
esp_mqtt_client_subscribe
could be used to call this function.
- 参数
client -- MQTT client handle
topic -- topic filter to subscribe
qos -- Max qos level of the subscription
- 返回
message_id of the subscribe message on success -1 on failure -2 in case of full outbox.
-
int esp_mqtt_client_subscribe_multiple(esp_mqtt_client_handle_t client, const esp_mqtt_topic_t *topic_list, int size)
Subscribe the client to a list of defined topics with defined qos.
Notes:
Client must be connected to send subscribe message
This API is could be executed from a user task or from a MQTT event callback i.e. internal MQTT task (API is protected by internal mutex, so it might block if a longer data receive operation is in progress.
esp_mqtt_client_subscribe
could be used to call this function.
- 参数
client -- MQTT client handle
topic_list -- List of topics to subscribe
size -- size of topic_list
- 返回
message_id of the subscribe message on success -1 on failure -2 in case of full outbox.
-
int esp_mqtt_client_unsubscribe(esp_mqtt_client_handle_t client, const char *topic)
Unsubscribe the client from defined topic.
Notes:
Client must be connected to send unsubscribe message
It is thread safe, please refer to
esp_mqtt_client_subscribe_single
for details
- 参数
client -- MQTT client handle
topic --
- 返回
message_id of the subscribe message on success -1 on failure
-
int esp_mqtt_client_publish(esp_mqtt_client_handle_t client, const char *topic, const char *data, int len, int qos, int retain)
Client to send a publish message to the broker.
Notes:
This API might block for several seconds, either due to network timeout (10s) or if publishing payloads longer than internal buffer (due to message fragmentation)
Client doesn't have to be connected for this API to work, enqueueing the messages with qos>1 (returning -1 for all the qos=0 messages if disconnected). If MQTT_SKIP_PUBLISH_IF_DISCONNECTED is enabled, this API will not attempt to publish when the client is not connected and will always return -1.
It is thread safe, please refer to
esp_mqtt_client_subscribe
for details
- 参数
client -- MQTT client handle
topic -- topic string
data -- payload string (set to NULL, sending empty payload message)
len -- data length, if set to 0, length is calculated from payload string
qos -- QoS of publish message
retain -- retain flag
- 返回
message_id of the publish message (for QoS 0 message_id will always be zero) on success. -1 on failure, -2 in case of full outbox.
-
int esp_mqtt_client_enqueue(esp_mqtt_client_handle_t client, const char *topic, const char *data, int len, int qos, int retain, bool store)
Enqueue a message to the outbox, to be sent later. Typically used for messages with qos>0, but could be also used for qos=0 messages if store=true.
This API generates and stores the publish message into the internal outbox and the actual sending to the network is performed in the mqtt-task context (in contrast to the esp_mqtt_client_publish() which sends the publish message immediately in the user task's context). Thus, it could be used as a non blocking version of esp_mqtt_client_publish().
- 参数
client -- MQTT client handle
topic -- topic string
data -- payload string (set to NULL, sending empty payload message)
len -- data length, if set to 0, length is calculated from payload string
qos -- QoS of publish message
retain -- retain flag
store -- if true, all messages are enqueued; otherwise only QoS 1 and QoS 2 are enqueued
- 返回
message_id if queued successfully, -1 on failure, -2 in case of full outbox.
-
esp_err_t esp_mqtt_client_destroy(esp_mqtt_client_handle_t client)
Destroys the client handle.
Notes:
Cannot be called from the MQTT event handler
- 参数
client -- MQTT client handle
- 返回
ESP_OK ESP_ERR_INVALID_ARG on wrong initialization
-
esp_err_t esp_mqtt_set_config(esp_mqtt_client_handle_t client, const esp_mqtt_client_config_t *config)
Set configuration structure, typically used when updating the config (i.e. on "before_connect" event.
- 参数
client -- MQTT client handle
config -- MQTT configuration structure
- 返回
ESP_ERR_NO_MEM if failed to allocate ESP_ERR_INVALID_ARG if conflicts on transport configuration. ESP_OK on success
-
esp_err_t esp_mqtt_client_register_event(esp_mqtt_client_handle_t client, esp_mqtt_event_id_t event, esp_event_handler_t event_handler, void *event_handler_arg)
Registers MQTT event.
- 参数
client -- MQTT client handle
event -- event type
event_handler -- handler callback
event_handler_arg -- handlers context
- 返回
ESP_ERR_NO_MEM if failed to allocate ESP_ERR_INVALID_ARG on wrong initialization ESP_OK on success
-
esp_err_t esp_mqtt_client_unregister_event(esp_mqtt_client_handle_t client, esp_mqtt_event_id_t event, esp_event_handler_t event_handler)
Unregisters mqtt event.
- 参数
client -- mqtt client handle
event -- event ID
event_handler -- handler to unregister
- 返回
ESP_ERR_NO_MEM if failed to allocate ESP_ERR_INVALID_ARG on invalid event ID ESP_OK on success
-
int esp_mqtt_client_get_outbox_size(esp_mqtt_client_handle_t client)
Get outbox size.
- 参数
client -- MQTT client handle
- 返回
outbox size 0 on wrong initialization
-
esp_err_t esp_mqtt_dispatch_custom_event(esp_mqtt_client_handle_t client, esp_mqtt_event_t *event)
Dispatch user event to the mqtt internal event loop.
- 参数
client -- MQTT client handle
event -- MQTT event handle structure
- 返回
ESP_OK on success ESP_ERR_TIMEOUT if the event couldn't be queued (ref also CONFIG_MQTT_EVENT_QUEUE_SIZE)
Structures
-
struct esp_mqtt_error_codes
MQTT error code structure to be passed as a contextual information into ERROR event
Important: This structure extends
esp_tls_last_error
error structure and is backward compatible with it (so might be down-casted and treated asesp_tls_last_error
error, but recommended to update applications if used this way previously)Use this structure directly checking error_type first and then appropriate error code depending on the source of the error:
| error_type | related member variables | note | | MQTT_ERROR_TYPE_TCP_TRANSPORT | esp_tls_last_esp_err, esp_tls_stack_err, esp_tls_cert_verify_flags, sock_errno | Error reported from tcp_transport/esp-tls | | MQTT_ERROR_TYPE_CONNECTION_REFUSED | connect_return_code | Internal error reported from MQTT broker on connection |
Public Members
-
int esp_tls_stack_err
tls specific error code reported from underlying tls stack
-
int esp_tls_cert_verify_flags
tls flags reported from underlying tls stack during certificate verification
-
esp_mqtt_error_type_t error_type
error type referring to the source of the error
-
esp_mqtt_connect_return_code_t connect_return_code
connection refused error code reported from MQTT* broker on connection
-
int esp_transport_sock_errno
errno from the underlying socket
-
int esp_tls_stack_err
-
struct esp_mqtt_event_t
MQTT event configuration structure
Public Members
-
esp_mqtt_event_id_t event_id
MQTT event type
-
esp_mqtt_client_handle_t client
MQTT client handle for this event
-
char *data
Data associated with this event
-
int data_len
Length of the data for this event
-
int total_data_len
Total length of the data (longer data are supplied with multiple events)
-
int current_data_offset
Actual offset for the data associated with this event
-
char *topic
Topic associated with this event
-
int topic_len
Length of the topic for this event associated with this event
-
int msg_id
MQTT messaged id of message
-
int session_present
MQTT session_present flag for connection event
-
esp_mqtt_error_codes_t *error_handle
esp-mqtt error handle including esp-tls errors as well as internal MQTT errors
-
bool retain
Retained flag of the message associated with this event
-
int qos
QoS of the messages associated with this event
-
bool dup
dup flag of the message associated with this event
-
esp_mqtt_protocol_ver_t protocol_ver
MQTT protocol version used for connection, defaults to value from menuconfig
-
esp_mqtt_event_id_t event_id
-
struct esp_mqtt_client_config_t
MQTT client configuration structure
Default values can be set via menuconfig
All certificates and key data could be passed in PEM or DER format. PEM format must have a terminating NULL character and the related len field set to 0. DER format requires a related len field set to the correct length.
Public Members
-
struct esp_mqtt_client_config_t::broker_t broker
Broker address and security verification
-
struct esp_mqtt_client_config_t::credentials_t credentials
User credentials for broker
-
struct esp_mqtt_client_config_t::session_t session
MQTT session configuration.
-
struct esp_mqtt_client_config_t::network_t network
Network configuration
-
struct esp_mqtt_client_config_t::task_t task
FreeRTOS task configuration.
-
struct esp_mqtt_client_config_t::buffer_t buffer
Buffer size configuration.
-
struct esp_mqtt_client_config_t::outbox_config_t outbox
Outbox configuration.
-
struct broker_t
Broker related configuration
Public Members
-
struct esp_mqtt_client_config_t::broker_t::address_t address
Broker address configuration
-
struct esp_mqtt_client_config_t::broker_t::verification_t verification
Security verification of the broker
-
struct address_t
Broker address
uri have precedence over other fields
If uri isn't set at least hostname, transport and port should.
-
struct verification_t
Broker identity verification
If fields are not set broker's identity isn't verified. it's recommended to set the options in this struct for security reasons.
Public Members
-
bool use_global_ca_store
Use a global ca_store, look esp-tls documentation for details.
-
esp_err_t (*crt_bundle_attach)(void *conf)
Pointer to ESP x509 Certificate Bundle attach function for the usage of certificate bundles.
-
const char *certificate
Certificate data, default is NULL, not required to verify the server.
-
size_t certificate_len
Length of the buffer pointed to by certificate.
-
const struct psk_key_hint *psk_hint_key
Pointer to PSK struct defined in esp_tls.h to enable PSK authentication (as alternative to certificate verification). PSK is enabled only if there are no other ways to verify broker.
-
bool skip_cert_common_name_check
Skip any validation of server certificate CN field, this reduces the security of TLS and makes the MQTT client susceptible to MITM attacks
-
const char **alpn_protos
NULL-terminated list of supported application protocols to be used for ALPN
-
const char *common_name
Pointer to the string containing server certificate common name. If non-NULL, server certificate CN must match this name, If NULL, server certificate CN must match hostname. This is ignored if skip_cert_common_name_check=true.
-
bool use_global_ca_store
-
struct esp_mqtt_client_config_t::broker_t::address_t address
-
struct buffer_t
Client buffer size configuration
Client have two buffers for input and output respectivelly.
-
struct credentials_t
Client related credentials for authentication.
Public Members
-
const char *username
MQTT username
-
const char *client_id
Set MQTT client identifier. Ignored if set_null_client_id == true If NULL set the default client id. Default client id is
ESP32_CHIPID%
whereCHIPID%
are last 3 bytes of MAC address in hex format
-
bool set_null_client_id
Selects a NULL client id
-
struct esp_mqtt_client_config_t::credentials_t::authentication_t authentication
Client authentication
-
struct authentication_t
Client authentication
Fields related to client authentication by broker
For mutual authentication using TLS, user could select certificate and key, secure element or digital signature peripheral if available.
Public Members
-
const char *password
MQTT password
-
const char *certificate
Certificate for ssl mutual authentication, not required if mutual authentication is not needed. Must be provided with
key
.
-
size_t certificate_len
Length of the buffer pointed to by certificate.
-
const char *key
Private key for SSL mutual authentication, not required if mutual authentication is not needed. If it is not NULL, also
certificate
has to be provided.
-
size_t key_len
Length of the buffer pointed to by key.
-
const char *key_password
Client key decryption password, not PEM nor DER, if provided
key_password_len
must be correctly set.
-
int key_password_len
Length of the password pointed to by
key_password
-
bool use_secure_element
Enable secure element, available in ESP32-ROOM-32SE, for SSL connection
-
void *ds_data
Carrier of handle for digital signature parameters, digital signature peripheral is available in some Espressif devices.
-
const char *password
-
const char *username
-
struct network_t
Network related configuration
Public Members
-
int reconnect_timeout_ms
Reconnect to the broker after this value in miliseconds if auto reconnect is not disabled (defaults to 10s)
-
int timeout_ms
Abort network operation if it is not completed after this value, in milliseconds (defaults to 10s).
-
int refresh_connection_after_ms
Refresh connection after this value (in milliseconds)
-
bool disable_auto_reconnect
Client will reconnect to server (when errors/disconnect). Set
disable_auto_reconnect=true
to disable
-
esp_transport_handle_t transport
Custom transport handle to use. Warning: The transport should be valid during the client lifetime and is destroyed when esp_mqtt_client_destroy is called.
-
struct ifreq *if_name
The name of interface for data to go through. Use the default interface without setting
-
int reconnect_timeout_ms
-
struct outbox_config_t
Client outbox configuration options.
Public Members
-
uint64_t limit
Size limit for the outbox in bytes.
-
uint64_t limit
-
struct session_t
MQTT Session related configuration
Public Members
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struct esp_mqtt_client_config_t::session_t::last_will_t last_will
Last will configuration
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bool disable_clean_session
MQTT clean session, default clean_session is true
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int keepalive
MQTT keepalive, default is 120 seconds When configuring this value, keep in mind that the client attempts to communicate with the broker at half the interval that is actually set. This conservative approach allows for more attempts before the broker's timeout occurs
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bool disable_keepalive
Set
disable_keepalive=true
to turn off keep-alive mechanism, keepalive is active by default. Note: setting the config valuekeepalive
to0
doesn't disable keepalive feature, but uses a default keepalive period
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esp_mqtt_protocol_ver_t protocol_ver
MQTT protocol version used for connection.
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int message_retransmit_timeout
timeout for retransmitting of failed packet
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struct last_will_t
Last Will and Testament message configuration.
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struct esp_mqtt_client_config_t::session_t::last_will_t last_will
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struct task_t
Client task configuration
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struct topic_t
Topic definition struct
Macros
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MQTT_ERROR_TYPE_ESP_TLS
MQTT_ERROR_TYPE_TCP_TRANSPORT error type hold all sorts of transport layer errors, including ESP-TLS error, but in the past only the errors from MQTT_ERROR_TYPE_ESP_TLS layer were reported, so the ESP-TLS error type is re-defined here for backward compatibility
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esp_mqtt_client_subscribe(client_handle, topic_type, qos_or_size)
Convenience macro to select subscribe function to use.
Notes:
Usage of
esp_mqtt_client_subscribe_single
is the same as previous esp_mqtt_client_subscribe, refer to it for details.
- 参数
client_handle -- MQTT client handle
topic_type -- Needs to be char* for single subscription or
esp_mqtt_topic_t
for multiple topicsqos_or_size -- It's either a qos when subscribing to a single topic or the size of the subscription array when subscribing to multiple topics.
- 返回
message_id of the subscribe message on success -1 on failure -2 in case of full outbox.
Type Definitions
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typedef struct esp_mqtt_client *esp_mqtt_client_handle_t
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typedef enum esp_mqtt_event_id_t esp_mqtt_event_id_t
MQTT event types.
User event handler receives context data in
esp_mqtt_event_t
structure withclient - MQTT client handle
various other data depending on event type
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typedef enum esp_mqtt_connect_return_code_t esp_mqtt_connect_return_code_t
MQTT connection error codes propagated via ERROR event
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typedef enum esp_mqtt_error_type_t esp_mqtt_error_type_t
MQTT connection error codes propagated via ERROR event
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typedef enum esp_mqtt_transport_t esp_mqtt_transport_t
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typedef enum esp_mqtt_protocol_ver_t esp_mqtt_protocol_ver_t
MQTT protocol version used for connection
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typedef struct esp_mqtt_error_codes esp_mqtt_error_codes_t
MQTT error code structure to be passed as a contextual information into ERROR event
Important: This structure extends
esp_tls_last_error
error structure and is backward compatible with it (so might be down-casted and treated asesp_tls_last_error
error, but recommended to update applications if used this way previously)Use this structure directly checking error_type first and then appropriate error code depending on the source of the error:
| error_type | related member variables | note | | MQTT_ERROR_TYPE_TCP_TRANSPORT | esp_tls_last_esp_err, esp_tls_stack_err, esp_tls_cert_verify_flags, sock_errno | Error reported from tcp_transport/esp-tls | | MQTT_ERROR_TYPE_CONNECTION_REFUSED | connect_return_code | Internal error reported from MQTT broker on connection |
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typedef struct esp_mqtt_event_t esp_mqtt_event_t
MQTT event configuration structure
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typedef esp_mqtt_event_t *esp_mqtt_event_handle_t
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typedef struct esp_mqtt_client_config_t esp_mqtt_client_config_t
MQTT client configuration structure
Default values can be set via menuconfig
All certificates and key data could be passed in PEM or DER format. PEM format must have a terminating NULL character and the related len field set to 0. DER format requires a related len field set to the correct length.
Enumerations
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enum esp_mqtt_event_id_t
MQTT event types.
User event handler receives context data in
esp_mqtt_event_t
structure withclient - MQTT client handle
various other data depending on event type
Values:
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enumerator MQTT_EVENT_ANY
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enumerator MQTT_EVENT_ERROR
on error event, additional context: connection return code, error handle from esp_tls (if supported)
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enumerator MQTT_EVENT_CONNECTED
connected event, additional context: session_present flag
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enumerator MQTT_EVENT_DISCONNECTED
disconnected event
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enumerator MQTT_EVENT_SUBSCRIBED
subscribed event, additional context:
msg_id message id
error_handle
error_type
in case subscribing faileddata pointer to broker response, check for errors.
data_len length of the data for this event
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enumerator MQTT_EVENT_UNSUBSCRIBED
unsubscribed event, additional context: msg_id
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enumerator MQTT_EVENT_PUBLISHED
published event, additional context: msg_id
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enumerator MQTT_EVENT_DATA
data event, additional context:
msg_id message id
topic pointer to the received topic
topic_len length of the topic
data pointer to the received data
data_len length of the data for this event
current_data_offset offset of the current data for this event
total_data_len total length of the data received
retain retain flag of the message
qos QoS level of the message
dup dup flag of the message Note: Multiple MQTT_EVENT_DATA could be fired for one message, if it is longer than internal buffer. In that case only first event contains topic pointer and length, other contain data only with current data length and current data offset updating.
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enumerator MQTT_EVENT_BEFORE_CONNECT
The event occurs before connecting
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enumerator MQTT_EVENT_DELETED
Notification on delete of one message from the internal outbox, if the message couldn't have been sent and acknowledged before expiring defined in OUTBOX_EXPIRED_TIMEOUT_MS. (events are not posted upon deletion of successfully acknowledged messages)
This event id is posted only if MQTT_REPORT_DELETED_MESSAGES==1
Additional context: msg_id (id of the deleted message).
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enumerator MQTT_USER_EVENT
Custom event used to queue tasks into mqtt event handler All fields from the esp_mqtt_event_t type could be used to pass an additional context data to the handler.
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enum esp_mqtt_connect_return_code_t
MQTT connection error codes propagated via ERROR event
Values:
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enumerator MQTT_CONNECTION_ACCEPTED
Connection accepted
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enumerator MQTT_CONNECTION_REFUSE_PROTOCOL
MQTT connection refused reason: Wrong protocol
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enumerator MQTT_CONNECTION_REFUSE_ID_REJECTED
MQTT connection refused reason: ID rejected
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enumerator MQTT_CONNECTION_REFUSE_SERVER_UNAVAILABLE
MQTT connection refused reason: Server unavailable
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enumerator MQTT_CONNECTION_REFUSE_BAD_USERNAME
MQTT connection refused reason: Wrong user
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enumerator MQTT_CONNECTION_REFUSE_NOT_AUTHORIZED
MQTT connection refused reason: Wrong username or password
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enumerator MQTT_CONNECTION_ACCEPTED
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enum esp_mqtt_error_type_t
MQTT connection error codes propagated via ERROR event
Values:
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enumerator MQTT_ERROR_TYPE_NONE
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enumerator MQTT_ERROR_TYPE_TCP_TRANSPORT
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enumerator MQTT_ERROR_TYPE_CONNECTION_REFUSED
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enumerator MQTT_ERROR_TYPE_SUBSCRIBE_FAILED
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enumerator MQTT_ERROR_TYPE_NONE
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enum esp_mqtt_transport_t
Values:
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enumerator MQTT_TRANSPORT_UNKNOWN
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enumerator MQTT_TRANSPORT_OVER_TCP
MQTT over TCP, using scheme:
MQTT
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enumerator MQTT_TRANSPORT_OVER_SSL
MQTT over SSL, using scheme:
MQTTS
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enumerator MQTT_TRANSPORT_OVER_WS
MQTT over Websocket, using scheme::
ws
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enumerator MQTT_TRANSPORT_OVER_WSS
MQTT over Websocket Secure, using scheme:
wss
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enumerator MQTT_TRANSPORT_UNKNOWN