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PUBACK

The acknowledgement a receiver sends back for a QoS 1 message.

PUBACK is the packet that acknowledges a QoS 1 PUBLISH; until it arrives the sender keeps the message and resends it with the DUP flag set.

Examples

  • A QoS 1 PUBLISH from the sensor is answered by one PUBACK carrying the same packet identifier, which is why QoS 1 costs two packets per message.

  • If the PUBACK is lost, the sender resends the PUBLISH, so the reading may arrive twice.

See also

quality of service acknowledgement at-least-once delivery
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