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CoAP server example

(See the README.md file in the upper level 'examples' directory for more information about examples.)
This CoAP server example is adaptation of one of the libcoap example.

CoAP server example would startup a daemon task, receive data from CoAP client and transmit data to CoAP client.

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things.
The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation.

please refer to RFC7252 for more details.

How to use example

Configure the project

make menuconfig

Set default serial port under Serial Flasher config
Set WiFi SSID under Example Configuration
Set WiFi Password under Example Configuration

Build and Flash

Build the project and flash it to the board, then run monitor tool to view serial output:

make -j4 flash monitor

(To exit the serial monitor, type Ctrl-].)

See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

Example Output

current CoAP server would startup a daemon task,
and the log is such as the following:

...
I (332) wifi: mode : sta (30:ae:a4:04:1b:7c)
I (1672) wifi: n:11 0, o:1 0, ap:255 255, sta:11 0, prof:1
I (1672) wifi: state: init -> auth (b0)
I (1682) wifi: state: auth -> assoc (0)
I (1692) wifi: state: assoc -> run (10)
I (1692) wifi: connected with huawei_cw, channel 11
I (1692) wifi: pm start, type: 1

I (2622) event: sta ip: 192.168.3.84, mask: 255.255.255.0, gw: 192.168.3.1
I (2622) CoAP_server: Connected to AP
...

if a CoAP client query /Espressif resource, CoAP server would return "no data"
until a CoAP client does a PUT with some data.

libcoap Documentation

This can be found at https://libcoap.net/doc/reference/4.2.0/

Troubleshooting

Please make sure CoAP client fetchs or puts data under path: /Espressif or fetches /.well-known/core
libcoap logging can be increased by changing #define COAP_LOGGING_LEVEL 0 to #define COAP_LOGGING_LEVEL 9

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