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heartbeat

A small message a device sends on a schedule just to say it is still alive.

A heartbeat is a periodic liveness message; a missed run of heartbeats marks the device as unhealthy or offline, independently of the broker's keepalive.

Examples

  • A node publishes a heartbeat from loop() every 60 s; if loop() hangs on a dead sensor, keepalive pings continue but the heartbeat stops, and the back end notices.

See also

keepalive last will observability
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