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Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

client

Any program or device that connects to the broker to publish or subscribe.

An MQTT client is any connection to the broker -- a sensor, a dashboard, a back-end service -- identified by its client ID; publishers and subscribers are both clients.

Examples

  • The greenhouse sensor, a phone app and a dashboard are all MQTT clients: each connects to the broker, none to each other.

  • mosquitto_sub and mosquitto_pub are command-line MQTT clients for testing.

See also

broker MQTT client ID publish/subscribe
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