read

Read available messages from MQTT topic

Since R2022a

Syntax

read(mqttClient)

mqttMsg = read(mqttClient,Topic=mqttTopic)

Description

mqttMsg = read(mqttClient) reads all available messages from all subscribed topic in the specified MQTT client. This action flushes the messages so they cannot be read again.

mqttMsg = read(mqttClient,Topic=mqttTopic) reads all available messages from the specified MQTT topic among the topics that mqttClient is subscribed to.

Examples

Read Messages from MQTT Topics

Create a nonsecure MQTT client connection to a HiveMQ public broker with default settings.

mqttClient = mqttclient("tcp://broker.hivemq.com");

Subscribe to an MQTT topic.

subscribe(mqttClient,"TopMW01");

Read all available messages from a specific subscribed topic.

mqttMsg = read(mqttClient,Topic="TopMW01");

Read all available messages from all subscribed topics.

mqttMsg = read(mqttClient)

mqttMsg =

  2×2 timetable

            Time              Topic           Data      
    ____________________    _________    _______________

    14-Dec-2021 16:00:37    "TopMW01"    "Hello World 1"
    14-Dec-2021 16:00:41    "TopMW01"    "Hello World 2"

Programmatically access the first message.

mqttMsg.Data(1)

ans = 

    "Hello World 1"

Input Arguments

mqttClient — MQTT client

Client object

MQTT client specified as an icomm.mqtt.Client object, created with the mqttclient function.

Example: mqttClient = mqttclient()

Data Types: object

mqttTopic — MQTT topic

string | char

MQTT topic to read messages from, specified as a string or character vector.

Example: "trubits/mqTop48"

Data Types: string | char

Output Arguments

mqttMsg — Messages read from MQTT topics

timetable

Messages read from MQTT topics, returned as a timetable of messages.

Version History

Introduced in R2022a