* MQTT: handle large/chunked/fragmented messages properly
If a message spans multiple TCP packets it must be buffered before
delivered to LUA. Prior code did not do this at all, so this "patch"
really adds proper handling of fragmented MQTT packets.
This could also occur if multiple small messages was sent in a
single TCP packet, and the last message did not completely fit in that
packet.
Introduces a new option to the mqtt.Client constructor:
max_publish_length which defaults to 1024
Introduces a new 'overflow' callback.
Fixes issue #2308 and proper fix for PR #2544.
* mqtt.md: clarified heap allocation
* mqtt: ensure ack is sent for overflowed publish
If QoS is used we should still acknowledge that we received it, or server might retransmit it later.
- Process the CONNACK message received from the broker after Connect
- Provide feedback to Lua via failure callback on client:connect()
- Also provide failure information for other situations not covered by CONNACK
