Internal tcp_transport functions could now use custom socket operations.
This is used for WebSocket transport, when we typically wait for clean
connection closure, i.e. selecting for read/error with expected errno or
recv size=0 while socket readable (=connection terminated by FIN flag)
tcp-transport component did not support wait forever. this update uses value of -1 to request this state.
websocket client uses timeouts in RTOS ticks. fixed recalculation to ms (including special value of -1) to use correctly tcp-transport component
Closes https://github.com/espressif/esp-idf/issues/4316
tcp_transport component used public header files such as 'transport.h', etc. which are too generic and might collide with user or user libraries headers
This change closes#2417
added docs and tests for mqtt library, small fixes (removed warnings, option for custom outbox, websocket bug fixed for longer transports). refactored to use common tcp_transport component, support for CMake build system.
Closes#2108
