unsubscribe

Unsubscribe from MQTT topics

Since R2022a

Syntax

unsubscribe(mqttClient)

unsubscribe(mqttClient,Topic=mqttTopic)

Description

unsubscribe(mqttClient) unsubscribes the MQTT client from all its subscribed topics.

unsubscribe(mqttClient,Topic=mqttTopic) unsubscribes the MQTT client from the topic specified in mqttTopic.

Examples

Unsubscribe from MQTT Topics

View the subscriptions of a client.

mqttClient.Subscriptions

ans =

  3×3 table

          Topic          QualityOfService      Callback   
    _________________    ________________    _____________

    "trubits/mqTop48"           0            ""           
    "trubits/mqTmp52"           2            ""           
    "trubits/mqTsp61"           0            "showmessage"

Unsubscribe from one topic.

unsubscribe(mqttClient,Topic="trubits/mqTsp61")
mqttClient.Subscriptions

ans =

  2×3 table

          Topic          QualityOfService    Callback
    _________________    ________________    ________

    "trubits/mqTop48"           0               ""   
    "trubits/mqTmp52"           2               ""

Unsubscribe from all remaining topics.

unsubscribe(mqttClient)
mqttClient.Subscriptions

ans =

  0×3 empty table

Unsubscribe Using Wildcard Topics

View the subscriptions of a client.

mqttClient.Subscriptions

ans =

  5×3 table

          Topic          QualityOfService      Callback   
    _________________    ________________    _____________

    "MATLAB/104/mqTop48"           0               ""   
    "MATLAB/105/mqTop48"           0               ""   
    "MATLAB/105/mqTmp52"           0               ""   
    "MATLAB/105/mqTsp61"           0               ""   
    "MATLAB/106/mqTrp74"           0               ""   

Unsubscribe using a single-level wildcard.

unsubscribe(mqttClient,Topic="MATLAB/+/mqTop48")
mqttClient.Subscriptions

ans =

  3×3 table

          Topic          QualityOfService    Callback
    _________________    ________________    ________

    "MATLAB/105/mqTmp52"           0               ""   
    "MATLAB/105/mqTsp61"           0               ""   
    "MATLAB/106/mqTrp74"           0               ""  

Unsubscribe using a multi-level wildcard.

unsubscribe(mqttClient,Topic="MATLAB/#")
mqttClient.Subscriptions

ans =

  0×3 empty table

Input Arguments

mqttClient — MQTT client

Client object

MQTT client, specified as an icomm.mqtt.Client object. Create the client using the mqttclient function.

Example: mqttClient = mqttclient()

Data Types: object

mqttTopic — MQTT topic

string | character vector

MQTT topic to unsubscribe from, specified as a string or character vector. Specify a wildcard topic to unsubscribe from all topics under a certain hierarchy.

Example: "trubits/mqTop48"

Data Types: string | char

Version History

Introduced in R2022a

R2025a: Unsubscribe using wildcard topic

Use the unsubscribe function with a wildcard topic to unsubscribe from all topics under a certain hierarchy.