Message delivery retry
tchaloupka opened this issue · comments
Specs - Message delivery retry, Message ordering
When a Client reconnects with CleanSession set to 0, both the Client and Server MUST re-send any unacknowledged PUBLISH Packets (where QoS > 0) and PUBREL Packets using their original Packet Identifiers.
This is the only circumstance where a Client or Server is REQUIRED to redeliver messages.
The DUP flag MUST be set to 1 by the Client or Server when it attempts to re-deliver a PUBLISH Packet . The DUP flag MUST be set to 0 for all QoS 0 messages