Mqtt notes
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Contents
Overview
Notes on MQTT
2021-12-20 - On devzone.nordicsemi.com creating public forum post with title "aws_iot MQTT subscriber keep alive", following suggested posts as solutions come up:
-
A possible Zephyr k_work_submit() solution:
^ Tau and AT, iDRX and cDRX parameters
In response to post on Nordic Devzone:
^ MQTT Persistent Sessions References
^ aws_iot Run-time Message Excerpts
Looks like in Nordic Semi's aws_iot sample app, the following enumerated events represent a firmware instance receiving subscribed messages from an MQTT broker:
- 1108 DEV - aws_iot event handler called, AWS_IOT_EVT_READY - 1108 DEV - aws_iot event handler called, AWS_IOT_EVT_DATA_RECEIVED
s3://iot-poc/hello/world/
Ah, trouble when attempting to add MQTT topics:
*** Booting Zephyr OS build v2.6.0-rc1-ncs1 *** I: Modem library is not yet initialized, AT commands not sent I: Configuration of MAGPIO and COEX0 is left to drivers The AWS IoT sample started, version: v1.0.0 ZZZ ZZZ ZZZ ZZZ - preparing to subscribe to hello/world topic, ZZZ ZZZ ZZZ - calling routine to subscribe to MQTT topics . . . ZZZ E: Application subscription list count mismatch aws_iot_subscription_topics_add, error: -122 ZZZ ZZZ ZZZ ZZZ Adding application specific topics failed, error: -122 Summary of callback pointers for 'set flag' events:
Appears to come from `./nrf/subsys/net/lib/aws_iot/src/aws_iot.c:1168: LOG_ERR("Application subscription list count mismatch");`
Note 3 - code excert from `nrf/subsys/net/lib/aws_iot/src/aws_iot.c`:
689 if (!mqtt_evt->param.connack.session_present_flag ||
690 IS_ENABLED(CONFIG_MQTT_CLEAN_SESSION)) {
691 err = topic_subscribe();
692
693 if (err < 0) {
694 aws_iot_evt.type = AWS_IOT_EVT_ERROR;
695 aws_iot_evt.data.err = err;
696 aws_iot_notify_event(&aws_iot_evt);
697 break;
698 }
699 if (err == 0) {
700 /* There were not topics to subscribe to. */
701 aws_iot_evt.type = AWS_IOT_EVT_READY;
702 aws_iot_notify_event(&aws_iot_evt);
703 } /* else: wait for SUBACK */
704 } else {
705 /* pre-existing session:
706 * subscription is already established.
707 */
708 aws_iot_evt.type = AWS_IOT_EVT_READY;
709 aws_iot_notify_event(&aws_iot_evt);
710
711 if (IS_ENABLED(
951 #if defined(CONFIG_AWS_IOT_LAST_WILL)
952 static struct mqtt_topic last_will_topic = {
953 .topic.utf8 = CONFIG_AWS_IOT_LAST_WILL_TOPIC,
954 .topic.size = sizeof(CONFIG_AWS_IOT_LAST_WILL_TOPIC) - 1,
955 .qos = MQTT_QOS_0_AT_MOST_ONCE
956 };
957
958 static struct mqtt_utf8 last_will_message = {
959 .utf8 = CONFIG_AWS_IOT_LAST_WILL_MESSAGE,
960 .size = sizeof(CONFIG_AWS_IOT_LAST_WILL_MESSAGE) - 1
961 };
962
963 client->will_topic = &last_will_topic;
964 client->will_message = &last_will_message;
965 #endif
966
967 static sec_tag_t sec_tag_list[] = { CONFIG_AWS_IOT_SEC_TAG };
968 struct mqtt_sec_config *tls_cfg = &(client->transport).tls.config;
969
970 tls_cfg->peer_verify = 2;
971 tls_cfg->cipher_count = 0;
972 tls_cfg->cipher_list = NULL;
973 tls_cfg->sec_tag_count = ARRAY_SIZE(sec_tag_list);
974 tls_cfg->sec_tag_list = sec_tag_list;
975 tls_cfg->hostname = CONFIG_AWS_IOT_BROKER_HOST_NAME;
976 tls_cfg->session_cache = TLS_SESSION_CACHE_DISABLED;
977
978 #if !defined(CONFIG_NRF_MODEM_LIB)
979 err = certificates_provision();
980 if (err) {
981 LOG_ERR("Could not provision certificates, error: %d", err);
982 return err;
983 }
984 #endif /* !defined(CONFIG_NRF_MODEM_LIB) */
985
986 return err;
987 }
z4-sandbox-kionix-work/nrf/subsys/net/lib/aws_iot/src$ grep -n 'struct mqtt_topic' ./*.*
451: const struct mqtt_topic aws_iot_rx_list[] = {
546: .list = (struct mqtt_topic *)&aws_iot_rx_list,
952: static struct mqtt_topic last_will_topic = {
edit point
./zephyr/include/net/mqtt.h:178:struct mqtt_topic {
/** @brief Abstracts UTF-8 encoded strings. */
struct mqtt_utf8 {
const uint8_t *utf8; /**< Pointer to UTF-8 string. */
uint32_t size; /**< Size of UTF string, in bytes. */
};
/** @brief Abstracts MQTT UTF-8 encoded topic that can be subscribed
* to or published.
*/
struct mqtt_topic {
/** Topic on to be published or subscribed to. */
struct mqtt_utf8 topic;
/** Quality of service requested for the subscription.
* @ref mqtt_qos for details.
*/
uint8_t qos;
};
A link to review:
2021-12-14 Tue
- https://forums.aws.amazon.com/index.jspa
- https://aws.amazon.com/blogs/iot/getting-started-mqtt-retained-messages-aws-iot-core/
- https://docs.aws.amazon.com/iot/latest/developerguide/mqtt.html#mqtt-retain
2021-12-08
* https://github.com/aws/aws-iot-device-sdk-embedded-C/blob/main/demos/mqtt/mqtt_demo_basic_tls/mqtt_demo_basic_tls.c
+++
* https://docs.aws.amazon.com/iot/latest/developerguide/topics.html
Unsorted references to MQTT:
# https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/net/mqtt_publisher/README.html # https://www.hivemq.com/blog/mqtt-essentials-part2-publish-subscribe/ # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/samples/index.html # https://www.circuito.io/blog/arduino-code/ # https://www.hivemq.com/blog/mqtt-essentials-part-7-persistent-session-queuing-messages/ # https://www.hivemq.com/blog/mqtt-essentials-part-3-client-broker-connection-establishment/
# https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/nrf/examples.html # https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/nrf/ug_tfm.html#ug-tfm # https://ci-builds.trustedfirmware.org/static-files/UxIoKYsDyPQ0ojvJOv9EX6-hZNDZd6IPGfcm05Bk1b0xNjM3MTA4NjMxODUxOjk6YW5vbnltb3VzOmpvYi90Zi1tLWJ1aWxkLWRvY3MtbmlnaHRseS9sYXN0U3RhYmxlQnVpbGQvYXJ0aWZhY3Q=/trusted-firmware-m/build/docs/user_guide/html/index.html
Nordic AWS FOTA example:
# https://developer.nordicsemi.com/nRF_Connect_SDK/doc/1.6.1/nrf/samples/nrf9160/aws_fota/README.html
^ successful publish to hello/world topic
Created JSON message but not publishing to AWS IoT broker,
- 1110 DEV - new file scoped flag for aws_iot holds 0,
message is: {
"version": "512",
"deviceType": "PulseV2",
"deviceSerialNumber": "352656101125105",
"state": {
"reported": {
"ts": 1639641106680,
"vrms": "0.406",
"alert_vrms_threshhold_1": "no_alert",
"latitude": "45.40494423760174",
"longitude": "-122.5310215439456",
"altitude": "0.0"
}
}
}
RRC mode: Connected
- 1108 DEV - aws_iot event handler called,
AWS_IOT_EVT_DATA_RECEIVED
Data received from AWS IoT console:
Topic: hello/world
Message: {
"version": "513",
"note": "test 010",
"KEYNAME001": "*** **** *** **** ***",
"KEYNAME002": "*** **** *** **** ***",
"KEYNAME003": "*** **** *** **** ***"
}
adm: power_time_domain=0.003, power_freq_domain=0.002, diff=0.001, ratio=1.604
- 1105 - calculated VRMS of 0.000000
- MARK 7 - at every 100 CLI loop iterations
button press count at 0
adm: power_time_domain=0.002, power_freq_domain=0.001, diff=0.001, ratio=1.631
- 1105 - calculated VRMS of 0.798562
RRC mode: Idle
