This takes the code up to the latest released version of libcoap.
As there have been API changes, coap_client and coap_server in
examples/protocols have been updated to use the new APIs.
Further information on the new libcoap APIs can be found at
https://libcoap.net/doc/reference/4.2.0/
coap_client has been updated to handle BLOCK2 responses from
"coap://californium.eclipse.org"
coap_client has been modified to only send out one request (and wait for
the response)
coap_server has been updated to support Observe subscriptions, and well as
adding in PUT and DELETE handlers to work on the Espressif resource
coap_server and coap_client have had their stack sizes increased.
port/coap_io.c has been added, a copy of libcoap/src/coap_io.c with support
added for systems that do not have RFC 3542 section 20 support.
port/coap_io_socket.c has been removed as a lot of the code is now
replicated in different libcoap files.
Once this PR is place, then adding in DTLS will be a lot simpler (as a
separate PR)
Signed-off-by: Jitin George <jitin@espressif.com>
Merges https://github.com/espressif/esp-idf/pull/3148
