Quite a few updates. Subscription feature is now working,
which is great. This has been tested with mosquitto broker
as well as Adafruit IO, and it works perfectly with both.
I tried to compile this project as a library (see the changes
to Makefile) but when I used that .a file in another project
the linking process failed. More research needed, I've never
tried to do that before.
I compressed some of the case statements in mqtt_send as they
are so similar, it's a waste of code space to duplicate them.
Disconnect and ping are identical except for one byte, and
unsubscribe and subscribe differ in only a few lines.
The data receive callback now prints information on what kind
of packet/data was received; again, mostly useful during
debugging, but the framework is there to expand it to do
useful things like triggering other tasks/timers, etc.
There is now a keepalive ping timer which keeps both the MQTT
and thus the TCP connection alive. It currently pings every 5
seconds, though I might change that closer to the timeout
maximum (50 seconds).
Signed-off-by: A.M. Rowsell <amrowsell@frozenelectronics.ca>
