5.5. mqtt_client — MQTT client

Source code: src/inet/mqtt_client.h, src/inet/mqtt_client.c

Test code: tst/inet/mqtt_client/main.c

Test coverage: src/inet/mqtt_client.c

Typedefs

typedef size_t (*mqtt_on_publish_t)(struct mqtt_client_t *client_p, const char *topic_p, void *chin_p, size_t size)

Prototype of the on-publish callback function.

Return
Number of bytes read from the input channel.
Parameters
  • client_p: The client.
  • topic_p: The received topic.
  • chin_p: The channel to read the value from.
  • size: Number of bytes of the value to read from chin_p.

typedef int (*mqtt_on_error_t)(struct mqtt_client_t *client_p, int error)

Prototype of the on-error callback function.

Return
zero(0) or nagative error code.
Parameters
  • client_p: The client.
  • error: The number of error that occured.

Enums

enum mqtt_client_state_t

Values:

mqtt_client_state_disconnected_t
mqtt_client_state_connected_t
mqtt_client_state_connecting_t
enum mqtt_qos_t

Quality of Service.

Values:

mqtt_qos_0_t = 0
mqtt_qos_1_t = 1
mqtt_qos_2_t = 2

Functions

int mqtt_client_init(struct mqtt_client_t *self_p, const char *name_p, struct log_object_t *log_object_p, void *chout_p, void *chin_p, mqtt_on_publish_t on_publish, mqtt_on_error_t on_error)

Initialize given MQTT client.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.
  • name_p: Name of the thread.
  • log_object_p: Log object.
  • chout_p: Output channel for client to server packets.
  • chin_p: Input channel for server to client packets.
  • on_publish: On-publish callback function. Called when the server publishes a message.
  • on_error: On-error callback function. Called when an error occurs.

void *mqtt_client_main(void *arg_p)

MQTT client thread.

Return
Never returns.
Parameters
  • arg_p: MQTT client.

int mqtt_client_connect(struct mqtt_client_t *self_p)

Establish a connection to the server.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.

int mqtt_client_disconnect(struct mqtt_client_t *self_p)

Disconnect from the server.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.

int mqtt_client_ping(struct mqtt_client_t *self_p)

Send a ping request to the server (broker) and wait for the ping response.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.

int mqtt_client_publish(struct mqtt_client_t *self_p, struct mqtt_application_message_t *message_p)

Publish given topic.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.
  • topic_p: Topic.
  • payload_p: Payload to publish. May be NULL.
  • payload_size: Number of bytes in the payload.

int mqtt_client_subscribe(struct mqtt_client_t *self_p, struct mqtt_application_message_t *message_p)

Subscribe to given message.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.
  • message_p: The message to subscribe to. The payload part of the message is not used. The topic may use wildcards, given that the server supports it.

int mqtt_client_unsubscribe(struct mqtt_client_t *self_p, struct mqtt_application_message_t *message_p)

Unsubscribe from given message.

Return
zero(0) or negative error code.
Parameters
  • self_p: MQTT client.
  • message_p: The message to unsubscribe from. Only the topic in the message is used.

struct mqtt_client_t
#include <mqtt_client.h>

MQTT client.

Public Members

const char *name_p
struct log_object_t *log_object_p
int state
int type
void *data_p
struct mqtt_client_t::@51 mqtt_client_t::message
void *out_p
void *in_p
struct mqtt_client_t::@52 mqtt_client_t::transport
struct queue_t out
struct queue_t in
struct mqtt_client_t::@53 mqtt_client_t::control
mqtt_on_publish_t on_publish
mqtt_on_error_t on_error
struct mqtt_application_message_t
#include <mqtt_client.h>

MQTT application message.

Public Members

const char *buf_p
size_t size
struct mqtt_application_message_t::@54 mqtt_application_message_t::topic
const void *buf_p
struct mqtt_application_message_t::@55 mqtt_application_message_t::payload
mqtt_qos_t qos