Chapter · MQTT
Delivery
Ordinary letters, registered mail and signed-for mail: QoS 0, 1 and 2, and why each hop has its own.
- 06QoS 0 and 14 minQoS 0 is an ordinary letter — posted, and never heard of again if the connection drops with it. QoS 1 is registered mail, posted again until a receipt comes back, so it arrives at least once, and sometimes twice.
- 07QoS 2, and each hop4 minQoS 2 delivers exactly once and pays four packets for it, where QoS 0 pays one. And QoS is agreed hop by hop — a subscriber gets the lower of the level a message was posted at and the level it asked for.
Start at 06 and read down — the order is the order things get easier in. Or take the one with your part in it; every article stands on its own, and links back to whatever it needs.