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net: mqtt: Add keep alive timeout helper

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Add function that returns remaining time until next keep alive message
shall be sent. Such function could be used for instance as a source
for `poll` timeout.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
This commit is contained in:
Robert Lubos 2020-01-17 13:03:16 +01:00 • committed by Jukka Rissanen
commit 20b1c695ab
2 changed files with 30 additions and 0 deletions
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12
include/net/mqtt.h
View file

@ -707,6 +707,18 @@ int mqtt_abort(struct mqtt_client *client);
*/
int mqtt_live(struct mqtt_client *client);
/**
* @brief Helper function to determine when next keep alive message should be
* sent. Can be used for instance as a source for `poll` timeout.
*
* @param[in] client Client instance for which the procedure is requested.
*
* @return Time in milliseconds until next keep alive message is expected to
* be sent. Function will return UINT32_MAX if keep alive messages are
* not enabled.
*/
u32_t mqtt_keepalive_time_left(const struct mqtt_client *client);
/**
* @brief Receive an incoming MQTT packet. The registered callback will be
* called with the packet content.

18
subsys/net/lib/mqtt/mqtt.c
View file

@ -597,6 +597,24 @@ int mqtt_live(struct mqtt_client *client)
return 0;
}
u32_t mqtt_keepalive_time_left(const struct mqtt_client *client)
{
u32_t elapsed_time = mqtt_elapsed_time_in_ms_get(
client->internal.last_activity);
u32_t keepalive_ms = 1000U * client->keepalive;
if (client->keepalive == 0) {
/* Keep alive not enabled. */
return UINT32_MAX;
}
if (keepalive_ms <= elapsed_time) {
return 0;
}
return keepalive_ms - elapsed_time;
}
int mqtt_input(struct mqtt_client *client)
{
int err_code = 0;