Add CoAP examples from ESP-IDF

.github/workflows/build_and_run_coap_examples.yml

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+name: Build and Run CoAP Examples
+
+on:
+  schedule:
+    - cron: '0 0 * * *' # Once per day at midnight
+  pull_request:
+    types: [opened, reopened, synchronize]
+    paths:
+      - 'coap/**'
+
+jobs:
+  build:
+    name: Build CoAP Client Example
+    strategy:
+      fail-fast: false
+      matrix:
+        idf_ver: ["release-v4.4", "release-v5.0", "latest"]
+        idf_target: ["esp32"]
+    runs-on: ubuntu-20.04
+    container: espressif/idf:${{ matrix.idf_ver }}
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: 'true'
+      - name: Build CoAP Client Example
+        env:
+          IDF_TARGET: ${{ matrix.idf_target }}
+        shell: bash
+        working-directory: coap/examples/coap_client
+        run: |
+          . ${IDF_PATH}/export.sh
+          export PEDANTIC_FLAGS="-DIDF_CI_BUILD -Werror -Werror=deprecated-declarations -Werror=unused-variable -Werror=unused-but-set-variable -Werror=unused-function"
+          export EXTRA_CFLAGS="${PEDANTIC_FLAGS} -Wstrict-prototypes"
+          export EXTRA_CXXFLAGS="${PEDANTIC_FLAGS}"
+          idf.py set-target esp32
+          cat sdkconfig.ci >> sdkconfig
+          idf.py build
+      - uses: actions/upload-artifact@v2
+        with:
+          name: coap_client_example_bin_${{ matrix.idf_ver }}
+          path: |
+            coap/examples/coap_client/build/bootloader/bootloader.bin
+            coap/examples/coap_client/build/partition_table/partition-table.bin
+            coap/examples/coap_client/build/coap_client.bin
+            coap/examples/coap_client/build/coap_client.elf
+            coap/examples/coap_client/build/flasher_args.json
+  run-target:
+    name: Run CoAP Client example on target
+    needs: build
+    strategy:
+      fail-fast: false
+      matrix:
+        idf_ver: ["release-v4.4", "release-v5.0", "latest"]
+        idf_target: ["esp32"]
+    runs-on: [self-hosted, ESP32-ETHERNET-KIT]
+    container:
+      image: python:3.7-buster
+      options: --privileged # Privileged mode has access to serial ports
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/download-artifact@v2
+        with:
+          name: coap_client_example_bin_${{ matrix.idf_ver }}
+          path: coap/examples/coap_client/build
+      - name: Install Python packages
+        env:
+          PIP_EXTRA_INDEX_URL: "https://dl.espressif.com/pypi/"
+        run: pip install --only-binary cryptography pytest-embedded pytest-embedded-serial-esp pytest-embedded-idf
+      - name: Run CoAP Client example
+        working-directory: coap/examples/coap_client
+        run: pytest --target=${{ matrix.idf_target }}

coap/examples/coap_client/CMakeLists.txt

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+# The following lines of boilerplate have to be in your project's CMakeLists
+# in this exact order for cmake to work correctly
+cmake_minimum_required(VERSION 3.16)
+
+# (Not part of the boilerplate)
+# This example uses an extra component for common functions such as Wi-Fi and Ethernet connection.
+set(EXTRA_COMPONENT_DIRS $ENV{IDF_PATH}/examples/common_components/protocol_examples_common)
+
+include($ENV{IDF_PATH}/tools/cmake/project.cmake)
+project(coap_client)

coap/examples/coap_client/README.md

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+| Supported Targets | ESP32 | ESP32-C2 | ESP32-C3 | ESP32-C6 | ESP32-H2 | ESP32-S2 | ESP32-S3 |
+| ----------------- | ----- | -------- | -------- | -------- | -------- | -------- | -------- |
+
+
+# CoAP client example
+
+(See the README.md file in the upper level 'examples' directory for more information about examples.)
+This CoAP client example is very simplified adaptation of one of the
+[libcoap](https://github.com/obgm/libcoap) examples.
+
+CoAP client example will connect your ESP32 device to a CoAP server, send off a GET request and
+fetch the response data from CoAP server.  The client can be extended to PUT / POST / DELETE requests,
+as well as supporting the Observer extensions [RFC7641](https://tools.ietf.org/html/rfc7641).
+
+If the URI is prefixed with coaps:// instead of coap://, then the CoAP client will attempt to use
+the DTLS protocol using the defined Pre-Shared Keys(PSK) or Public Key Infrastructure (PKI) which the
+CoAP server needs to know about.
+
+If the URI is prefixed with coap+tcp://, then the CoAP will try to use TCP for the communication.
+
+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](https://www.rfc-editor.org/rfc/pdfrfc/rfc7252.txt.pdf) for more details.
+
+## How to use example
+
+### Configure the project
+
+```
+idf.py menuconfig
+```
+
+Example Connection Configuration  --->
+ * Set WiFi SSID
+ * Set WiFi Password
+Component config  --->
+  CoAP Configuration  --->
+    * Set encryption method definition, PSK (default) or PKI
+    * Enable CoAP debugging if required
+    * Disable CoAP using TCP if this is not required (TCP needed for TLS)
+    * Disable CoAP server functionality to reduce code size
+Example CoAP Client Configuration  --->
+ * Set CoAP Target Uri
+ * If PSK, Set CoAP Preshared Key to use in connection to the server
+ * If PSK, Set CoAP PSK Client identity (username)
+
+### Build and Flash
+
+Build the project and flash it to the board, then run monitor tool to view serial output:
+
+```
+idf.py build
+idf.py -p PORT 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
+Prerequisite: we startup a CoAP server on coap server example,
+or use the default of coap://californium.eclipseprojects.io.
+
+and you could receive data from CoAP server if succeed,
+such as the following log:
+
+```
+...
+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 (2582) event: sta ip: 192.168.3.89, mask: 255.255.255.0, gw: 192.168.3.1
+I (2582) CoAP_client: Connected to AP
+I (2582) CoAP_client: DNS lookup succeeded. IP=35.185.40.182
+Received:
+****************************************************************
+CoAP RFC 7252                                  Cf 3.0.0-SNAPSHOT
+****************************************************************
+This server is using the Eclipse Californium (Cf) CoAP framework
+published under EPL+EDL: http://www.eclipse.org/californium/
+
+(c) 2014-2020 Institute for Pervasive Computing, ETH Zurich and others
+****************************************************************
+...
+```
+
+## libcoap Documentation
+This can be found at [libcoap Documentation](https://libcoap.net/documentation.html).
+The current API is 4.3.0.
+
+## libcoap Specific Issues
+These can be raised at [libcoap Issues](https://github.com/obgm/libcoap/issues).
+
+## Troubleshooting
+* Please make sure Target Url includes valid `host`, optional `port`,
+optional `path`, and begins with `coap://`, `coaps://`, `coap+tcp://` or `coaps+tcp://`
+(not all hosts support TCP/TLS including coap+tcp://californium.eclipseprojects.io).
+
+* CoAP logging can be enabled by running 'idf.py menuconfig -> Component config -> CoAP Configuration -> Enable CoAP debugging'
+and setting appropriate log level.  If Mbed TLS logging is required, this needs to be configured separately under mbedTLS
+Component Configuration and the CoAP logging level set to mbedTLS.
+
+* CoAP library does not support IPv6 only configuration, so it is necessary to enable `LWIP_IPv4`

coap/examples/coap_client/main/CMakeLists.txt

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+# Embed CA, certificate & key directly into binary
+idf_component_register(SRCS "coap_client_example_main.c"
+                    INCLUDE_DIRS "."
+                    EMBED_TXTFILES certs/coap_ca.pem certs/coap_client.crt certs/coap_client.key)

coap/examples/coap_client/main/Kconfig.projbuild

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+menu "Example CoAP Client Configuration"
+
+    # Hidden option that selects IPv4
+    config EXAMPLE_COAP_NEEDS_IPV4
+        bool
+        default true
+        select LWIP_IPV4
+
+    config EXAMPLE_TARGET_DOMAIN_URI
+        string "Target Uri"
+        default "coaps://californium.eclipseprojects.io"
+        help
+            Target uri for the example to use. Use coaps:// prefix for encrypted traffic
+            using Pre-Shared Key (PSK) or Public Key Infrastructure (PKI).
+
+    config EXAMPLE_COAP_PSK_KEY
+        string "Preshared Key (PSK) to used in the connection to the CoAP server"
+        depends on COAP_MBEDTLS_PSK
+        default "sesame"
+        help
+            The Preshared Key to use to encrypt the communicatons. The same key must be
+            used at both ends of the CoAP connection, and the CoaP client must request
+            an URI prefixed with coaps:// instead of coap:// for DTLS to be used.
+
+    config EXAMPLE_COAP_PSK_IDENTITY
+        string "PSK Client identity (username)"
+        depends on COAP_MBEDTLS_PSK
+        default "password"
+        help
+            The identity (or username) to use to identify to the CoAP server which
+            PSK key to use.
+
+endmenu

coap/examples/coap_client/main/certs/coap_ca.pem

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+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

coap/examples/coap_client/main/certs/coap_client.crt

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+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

coap/examples/coap_client/main/certs/coap_client.key

@@ -0,0 +1,4 @@
+-----BEGIN PRIVATE KEY-----
+MEECAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQcEJzAlAgEBBCBgNuyqKuRW0RxU1DVs
+aEpBPtVRVLRZYq6hZRzvZ6igBw==
+-----END PRIVATE KEY-----