|
#define | MQTT_PORT LWIP_IANA_PORT_MQTT |
|
#define | MQTT_TLS_PORT LWIP_IANA_PORT_SECURE_MQTT |
|
#define | mqtt_subscribe(client, topic, qos, cb, arg) mqtt_sub_unsub(client, topic, qos, cb, arg, 1) |
|
#define | mqtt_unsubscribe(client, topic, cb, arg) mqtt_sub_unsub(client, topic, 0, cb, arg, 0) |
|
|
err_t | mqtt_publish (mqtt_client_t *client, const char *topic, const void *payload, u16_t payload_length, u8_t qos, u8_t retain, mqtt_request_cb_t cb, void *arg) |
|
err_t | mqtt_sub_unsub (mqtt_client_t *client, const char *topic, u8_t qos, mqtt_request_cb_t cb, void *arg, u8_t sub) |
|
void | mqtt_set_inpub_callback (mqtt_client_t *client, mqtt_incoming_publish_cb_t pub_cb, mqtt_incoming_data_cb_t data_cb, void *arg) |
|
mqtt_client_t * | mqtt_client_new (void) |
|
void | mqtt_client_free (mqtt_client_t *client) |
|
err_t | mqtt_client_connect (mqtt_client_t *client, const ip_addr_t *ip_addr, u16_t port, mqtt_connection_cb_t cb, void *arg, const struct mqtt_connect_client_info_t *client_info) |
|
void | mqtt_disconnect (mqtt_client_t *client) |
|
u8_t | mqtt_client_is_connected (mqtt_client_t *client) |
|
MQTT client for lwIP
Author: Erik Andersson
Details of the MQTT protocol can be found at:
http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html
-----------------------------------------------------------------
1. Initial steps, reserve memory and make connection to server:
1.1: Provide storage
Static allocation:
mqtt_client_t static_client;
example_do_connect(&static_client);
Dynamic allocation:
mqtt_client_t *client = mqtt_client_new();
if(client != NULL) {
example_do_connect(&client);
}
1.2: Establish Connection with server
void example_do_connect(mqtt_client_t *client)
{
struct mqtt_connect_client_info_t ci;
err_t err;
/* Setup an empty client info structure */
memset(&ci, 0, sizeof(ci));
/* Minimal amount of information required is client identifier, so set it here */
ci.client_id = "lwip_test";
/* Initiate client and connect to server, if this fails immediately an error code is returned
otherwise mqtt_connection_cb will be called with connection result after attempting
to establish a connection with the server.
For now MQTT version 3.1.1 is always used */
err = mqtt_client_connect(client, ip_addr, MQTT_PORT, mqtt_connection_cb, 0, &ci);
/* For now just print the result code if something goes wrong */
if(err != ERR_OK) {
printf("mqtt_connect return %d\n", err);
}
}
Connection to server can also be probed by calling mqtt_client_is_connected(client)
-----------------------------------------------------------------
2. Implementing the connection status callback
static void mqtt_connection_cb(mqtt_client_t *client, void *arg, mqtt_connection_status_t status)
{
err_t err;
if(status == MQTT_CONNECT_ACCEPTED) {
printf("mqtt_connection_cb: Successfully connected\n");
/* Setup callback for incoming publish requests */
mqtt_set_inpub_callback(client, mqtt_incoming_publish_cb, mqtt_incoming_data_cb, arg);
/* Subscribe to a topic named "subtopic" with QoS level 1, call mqtt_sub_request_cb with result */
err = mqtt_subscribe(client, "subtopic", 1, mqtt_sub_request_cb, arg);
if(err != ERR_OK) {
printf("mqtt_subscribe return: %d\n", err);
}
} else {
printf("mqtt_connection_cb: Disconnected, reason: %d\n", status);
/* Its more nice to be connected, so try to reconnect */
example_do_connect(client);
}
}
static void mqtt_sub_request_cb(void *arg, err_t result)
{
/* Just print the result code here for simplicity,
normal behaviour would be to take some action if subscribe fails like
notifying user, retry subscribe or disconnect from server */
printf("Subscribe result: %d\n", result);
}
-----------------------------------------------------------------
3. Implementing callbacks for incoming publish and data
/* The idea is to demultiplex topic and create some reference to be used in data callbacks
Example here uses a global variable, better would be to use a member in arg
If RAM and CPU budget allows it, the easiest implementation might be to just take a copy of
the topic string and use it in mqtt_incoming_data_cb
*/
static int inpub_id;
static void mqtt_incoming_publish_cb(void *arg, const char *topic, u32_t tot_len)
{
printf("Incoming publish at topic %s with total length %u\n", topic, (unsigned int)tot_len);
/* Decode topic string into a user defined reference */
if(strcmp(topic, "print_payload") == 0) {
inpub_id = 0;
} else if(topic[0] == 'A') {
/* All topics starting with 'A' might be handled at the same way */
inpub_id = 1;
} else {
/* For all other topics */
inpub_id = 2;
}
}
static void mqtt_incoming_data_cb(void *arg, const u8_t *data, u16_t len, u8_t flags)
{
printf("Incoming publish payload with length %d, flags %u\n", len, (unsigned int)flags);
if(flags & MQTT_DATA_FLAG_LAST) {
/* Last fragment of payload received (or whole part if payload fits receive buffer
See MQTT_VAR_HEADER_BUFFER_LEN) */
/* Call function or do action depending on reference, in this case inpub_id */
if(inpub_id == 0) {
/* Don't trust the publisher, check zero termination */
if(data[len-1] == 0) {
printf("mqtt_incoming_data_cb: %s\n", (const char *)data);
}
} else if(inpub_id == 1) {
/* Call an 'A' function... */
} else {
printf("mqtt_incoming_data_cb: Ignoring payload...\n");
}
} else {
/* Handle fragmented payload, store in buffer, write to file or whatever */
}
}
-----------------------------------------------------------------
4. Using outgoing publish
void example_publish(mqtt_client_t *client, void *arg)
{
const char *pub_payload= "PubSubHubLubJub";
err_t err;
u8_t qos = 2; /* 0 1 or 2, see MQTT specification */
u8_t retain = 0; /* No don't retain such crappy payload... */
err = mqtt_publish(client, "pub_topic", pub_payload, strlen(pub_payload), qos, retain, mqtt_pub_request_cb, arg);
if(err != ERR_OK) {
printf("Publish err: %d\n", err);
}
}
/* Called when publish is complete either with sucess or failure */
static void mqtt_pub_request_cb(void *arg, err_t result)
{
if(result != ERR_OK) {
printf("Publish result: %d\n", result);
}
}
-----------------------------------------------------------------
5. Disconnecting
Simply call mqtt_disconnect(client)
◆ MQTT_PORT
Default MQTT port (non-TLS)
◆ mqtt_subscribe
#define mqtt_subscribe |
( |
|
client, |
|
|
|
topic, |
|
|
|
qos, |
|
|
|
cb, |
|
|
|
arg |
|
) |
| mqtt_sub_unsub(client, topic, qos, cb, arg, 1) |
◆ MQTT_TLS_PORT
◆ mqtt_unsubscribe
#define mqtt_unsubscribe |
( |
|
client, |
|
|
|
topic, |
|
|
|
cb, |
|
|
|
arg |
|
) |
| mqtt_sub_unsub(client, topic, 0, cb, arg, 0) |
◆ mqtt_connection_cb_t
Function prototype for mqtt connection status callback. Called when client has connected to the server after initiating a mqtt connection attempt by calling mqtt_client_connect() or when connection is closed by server or an error
- Parameters
-
client | MQTT client itself |
arg | Additional argument to pass to the callback function |
status | Connect result code or disconnection notification |
- See also
- mqtt_connection_status_t
◆ mqtt_incoming_data_cb_t
typedef void(* mqtt_incoming_data_cb_t) (void *arg, const u8_t *data, u16_t len, u8_t flags) |
Function prototype for MQTT incoming publish data callback function. Called when data arrives to a subscribed topic
- See also
- mqtt_subscribe
- Parameters
-
arg | Additional argument to pass to the callback function |
data | User data, pointed object, data may not be referenced after callback return, NULL is passed when all publish data are delivered |
len | Length of publish data fragment |
flags | MQTT_DATA_FLAG_LAST set when this call contains the last part of data from publish message |
◆ mqtt_incoming_publish_cb_t
typedef void(* mqtt_incoming_publish_cb_t) (void *arg, const char *topic, u32_t tot_len) |
Function prototype for MQTT incoming publish function. Called when an incoming publish arrives to a subscribed topic
- See also
- mqtt_subscribe
- Parameters
-
arg | Additional argument to pass to the callback function |
topic | Zero terminated Topic text string, topic may not be referenced after callback return |
tot_len | Total length of publish data, if set to 0 (no publish payload) data callback will not be invoked |
◆ mqtt_request_cb_t
typedef void(* mqtt_request_cb_t) (void *arg, err_t err) |
Function prototype for mqtt request callback. Called when a subscribe, unsubscribe or publish request has completed
- Parameters
-
arg | Pointer to user data supplied when invoking request |
err | ERR_OK on success ERR_TIMEOUT if no response was received within timeout, ERR_ABRT if (un)subscribe was denied |
◆ anonymous enum
Data callback flags
Enumerator |
---|
MQTT_DATA_FLAG_LAST | Flag set when last fragment of data arrives in data callback
|
◆ mqtt_connection_status_t
Connection status codes
Enumerator |
---|
MQTT_CONNECT_ACCEPTED | Accepted
|
MQTT_CONNECT_REFUSED_PROTOCOL_VERSION | Refused protocol version
|
MQTT_CONNECT_REFUSED_IDENTIFIER | Refused identifier
|
MQTT_CONNECT_REFUSED_SERVER | Refused server
|
MQTT_CONNECT_REFUSED_USERNAME_PASS | Refused user credentials
|
MQTT_CONNECT_REFUSED_NOT_AUTHORIZED_ | Refused not authorized
|
MQTT_CONNECT_DISCONNECTED | Disconnected
|
MQTT_CONNECT_TIMEOUT | Timeout
|
◆ mqtt_client_connect()
Connect to MQTT server
- Parameters
-
client | MQTT client |
ip_addr | Server IP |
port | Server port |
cb | Connection state change callback |
arg | User supplied argument to connection callback |
client_info | Client identification and connection options |
- Returns
- ERR_OK if successful,
- See also
- err_t enum for other results
◆ mqtt_client_free()
Free MQTT client instance
- Parameters
-
client | Pointer to instance to be freed |
◆ mqtt_client_is_connected()
Check connection with server
- Parameters
-
- Returns
- 1 if connected to server, 0 otherwise
◆ mqtt_client_new()
Create a new MQTT client instance
- Returns
- Pointer to instance on success, NULL otherwise
◆ mqtt_disconnect()
Disconnect from MQTT server
- Parameters
-
◆ mqtt_publish()
MQTT publish function.
- Parameters
-
client | MQTT client |
topic | Publish topic string |
payload | Data to publish (NULL is allowed) |
payload_length | Length of payload (0 is allowed) |
qos | Quality of service, 0 1 or 2 |
retain | MQTT retain flag |
cb | Callback to call when publish is complete or has timed out |
arg | User supplied argument to publish callback |
- Returns
- ERR_OK if successful ERR_CONN if client is disconnected ERR_MEM if short on memory
◆ mqtt_set_inpub_callback()
Set callback to handle incoming publish requests from server
- Parameters
-
client | MQTT client |
pub_cb | Callback invoked when publish starts, contain topic and total length of payload |
data_cb | Callback for each fragment of payload that arrives |
arg | User supplied argument to both callbacks |
◆ mqtt_sub_unsub()
MQTT subscribe/unsubscribe function.
- Parameters
-
client | MQTT client |
topic | topic to subscribe to |
qos | Quality of service, 0 1 or 2 (only used for subscribe) |
cb | Callback to call when subscribe/unsubscribe reponse is received |
arg | User supplied argument to publish callback |
sub | 1 for subscribe, 0 for unsubscribe |
- Returns
- ERR_OK if successful,
- See also
- err_t enum for other results