Add a WiFi Echo example for the ESP32 (project-chip#519)

* Add a WiFi Echo example for the ESP32

* Add missing newline

* Restyled by clang-format

* Move module include to the top

* Fix typo

* Retry if bind fails

* Fix nits

Co-authored-by: Restyled.io <commits@restyled.io>

.gitignore

@@ -27,3 +27,6 @@ third_party/nlfaultinjection/
 third_party/nlio/
 third_party/nlunit-test/
 third_party/mbedtls/
+
+# Example specific rules
+examples/**/sdkconfig

examples/wifi-echo/esp32/Makefile

@@ -0,0 +1,10 @@
+#
+# This is a project Makefile. It is assumed the directory this Makefile resides in is a
+# project subdirectory.
+#
+
+PROJECT_NAME := chip-wifi-echo
+
+EXTRA_COMPONENT_DIRS += $(PROJECT_PATH)/third_party/connectedhomeip/config/esp32/components
+
+include $(IDF_PATH)/make/project.mk

examples/wifi-echo/esp32/README.md

@@ -0,0 +1,84 @@
+# CHIP WiFi Echo Server Example
+
+A prototype appplication that uses CHIP to setup WiFi on the ESP32 and runs an
+Echo Server on a configured port. This example will evolve as more complex
+messaging is supported in CHIP.
+
+---
+
+-   [CHIP WiFi Echo Server Example](#chip-wifi-echo-server-example)
+-   [Supported Devices](#supported-devices)
+-   [Building the Example Application](#building-the-example-application)
+-   [Using the Echo Server](#using-the-echo-server)
+
+---
+
+## Supported Devices
+
+The CHIP demo application is intended to work on two categories of ESP32
+devices: the
+[ESP32-DevKitC](https://www.espressif.com/en/products/hardware/esp32-devkitc/overview),
+and the [M5Stack](http://m5stack.com). Support for the
+[M5Stack](http://m5stack.com) is still a Work in Progress.
+
+## Building the Example Application
+
+Building the example application requires the use of the Espressif ESP32 IoT
+Development Framework and the xtensa-esp32-elf toolchain.
+
+The VSCode devcontainer has these components pre-installed, so you can skip this
+step. To install these components manually, follow these steps:
+
+-   Clone the Expressif ESP-IDF and checkout version 4.0
+
+          $ mkdir ${HOME}/tools
+          $ cd ${HOME}/tools
+          $ git clone https://github.com/espressif/esp-idf.git
+          $ cd esp-idf
+          $ git checkout release/v4.0
+          $ git submodule update --init
+          $ export IDF_PATH=${HOME}/tools/esp-idf
+          $ ./install.sh
+
+To build the application, follow these steps:
+
+Currently building in VSCode _and_ deploying from native is not supported, so
+make sure the IDF_PATH has been exported(See the manual setup steps above).
+
+-   In the root of the example directory, use the `defconfig` make target to
+    configure the application with defaults.
+
+          $ idf make defconfig
+
+-   Run make to build the demo application
+
+          $ idf make
+
+-   After building the application, to flash it outside of VSCode, connect your
+    device via USB. Then run the following command to flash the demo application
+    onto the device and then monitor its output. If necessary, replace
+    `/dev/tty.SLAB_USBtoUART`(MacOS) with the correct USB device name for your
+    system(like `/dev/ttyUSB0` on Linux). Note that sometimes you might have to
+    press and hold the `boot` button on the device while it's trying to connect
+    before flashing.
+
+          $  make flash monitor ESPPORT=/dev/tty.SLAB_USBtoUART
+
+    Note: Some users might have to install the
+    [VCP driver](https://www.silabs.com/products/development-tools/software/usb-to-uart-bridge-vcp-drivers)
+    before the device shows up on `/dev/tty`.
+
+## Using the Echo Server
+
+After the application has been flashed, connect the ESP32's Soft-AP. It's
+usually something like `CHIP_DEMO-XXXX` where the last 4 digits are from the
+device's MAC address.
+
+Once you're connected, the server's IP can be found at the gateway address and
+at the listed port number(Default: `8000`).
+
+Then running the following command will ping the ESP32 and cause it to echo. If
+necessary replace the `192.168.4.1` with the address printed by the device in
+the monitor.
+
+          $ echo "Hello over IP" | nc -w1 -u 192.168.4.1 8000

examples/wifi-echo/esp32/idf.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+#
+#   Copyright (c) 2020 Project CHIP Authors
+#   All rights reserved.
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+# If this file is sourced, it exports a function called "idf" that initializes
+# the espressif environment via the espressive export.sh script and runs
+# a command presented as arguments
+#
+# This file can also be used as an executable
+me=${0##*/}
+die() {
+  echo "$me: *** ERROR: " "${*}"
+  exit 1
+}
+idf() {
+  [[ -d $IDF_PATH && -r $IDF_PATH/export.sh ]] || die "can't find IDF's export.sh"
+  . "$IDF_PATH/export.sh"
+  "$@"
+}
+if [[ ${0} == ${BASH_SOURCE[0]} ]]; then
+  idf "${@}"
+fi

examples/wifi-echo/esp32/main/EchoServer.cpp

@@ -0,0 +1,155 @@
+/*
+ *
+ *    Copyright (c) 2020 Project CHIP Authors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+#include <string.h>
+#include <sys/param.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "esp_system.h"
+#include "esp_wifi.h"
+#include "esp_event.h"
+#include "esp_log.h"
+#include "nvs_flash.h"
+#include "tcpip_adapter.h"
+
+#include "lwip/err.h"
+#include "lwip/sockets.h"
+#include "lwip/sys.h"
+#include <lwip/netdb.h>
+
+#define PORT CONFIG_ECHO_PORT
+#define RX_LEN 128
+#define ADDR_LEN 128
+
+static const char * TAG = "echo server";
+
+static void udp_server_task(void * pvParameters)
+{
+    char rx_buffer[RX_LEN];
+    char addr_str[ADDR_LEN];
+    int addr_family = (int) pvParameters;
+    int ip_protocol = 0;
+    struct sockaddr_in6 dest_addr;
+
+    while (1)
+    {
+
+        if (addr_family == AF_INET)
+        {
+            struct sockaddr_in * dest_addr_ip4 = (struct sockaddr_in *) &dest_addr;
+            dest_addr_ip4->sin_addr.s_addr     = htonl(INADDR_ANY);
+            dest_addr_ip4->sin_family          = AF_INET;
+            dest_addr_ip4->sin_port            = htons(PORT);
+            ip_protocol                        = IPPROTO_IP;
+        }
+        else if (addr_family == AF_INET6)
+        {
+            bzero(&dest_addr.sin6_addr.un, sizeof(dest_addr.sin6_addr.un));
+            dest_addr.sin6_family = AF_INET6;
+            dest_addr.sin6_port   = htons(PORT);
+            ip_protocol           = IPPROTO_IPV6;
+        }
+
+        int sock = socket(addr_family, SOCK_DGRAM, ip_protocol);
+        if (sock < 0)
+        {
+            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
+            break;
+        }
+        ESP_LOGI(TAG, "Socket created");
+
+#if defined(CONFIG_ECHO_IPV4) && defined(CONFIG_ECHO_IPV6)
+        if (addr_family == AF_INET6)
+        {
+            // Note that by default IPV6 binds to both protocols, it is must be disabled
+            // if both protocols used at the same time (used in CI)
+            int opt = 1;
+            setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+            setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt));
+        }
+#endif
+
+        int err = bind(sock, (struct sockaddr *) &dest_addr, sizeof(dest_addr));
+        if (err < 0)
+        {
+            ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
+            // Avoid looping hard if binding fails continuously
+            vTaskDelay(50 / portTICK_PERIOD_MS);
+            continue;
+        }
+        ESP_LOGI(TAG, "Socket bound, port %d", PORT);
+
+        while (1)
+        {
+
+            ESP_LOGI(TAG, "Waiting for data");
+            struct sockaddr_in6 source_addr; // Large enough for both IPv4 or IPv6
+            socklen_t socklen = sizeof(source_addr);
+            int len           = recvfrom(sock, rx_buffer, sizeof(rx_buffer) - 1, 0, (struct sockaddr *) &source_addr, &socklen);
+
+            // Error occurred during receiving
+            if (len < 0)
+            {
+                ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
+                break;
+            }
+            // Data received
+            else
+            {
+                // Get the sender's ip address as string
+                if (source_addr.sin6_family == PF_INET)
+                {
+                    inet_ntoa_r(((struct sockaddr_in *) &source_addr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);
+                }
+                else if (source_addr.sin6_family == PF_INET6)
+                {
+                    inet6_ntoa_r(source_addr.sin6_addr, addr_str, sizeof(addr_str) - 1);
+                }
+
+                rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string...
+                ESP_LOGI(TAG, "Received %d bytes from %s:", len, addr_str);
+                ESP_LOGI(TAG, "%s", rx_buffer);
+
+                int err = sendto(sock, rx_buffer, len, 0, (struct sockaddr *) &source_addr, sizeof(source_addr));
+                if (err < 0)
+                {
+                    ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
+                    break;
+                }
+            }
+        }
+
+        if (sock != -1)
+        {
+            ESP_LOGE(TAG, "Shutting down socket and restarting...");
+            shutdown(sock, 0);
+            close(sock);
+        }
+    }
+    vTaskDelete(NULL);
+}
+
+// The echo server assumes the platform's networking has been setup already
+void startServer(void)
+{
+#ifdef CONFIG_ECHO_IPV4
+    xTaskCreate(udp_server_task, "udp_server", 4096, (void *) AF_INET, 5, NULL);
+#endif
+#ifdef CONFIG_ECHO_IPV6
+    xTaskCreate(udp_server_task, "udp_server", 4096, (void *) AF_INET6, 5, NULL);
+#endif
+}

examples/wifi-echo/esp32/main/Kconfig.projbuild

@@ -0,0 +1,54 @@
+#
+#    Copyright (c) 2020 Project CHIP Authors
+#    All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License");
+#    you may not use this file except in compliance with the License.
+#    You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS,
+#    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#    See the License for the specific language governing permissions and
+#    limitations under the License.
+#
+#    Description:
+#      Configuration options CHIP ESP32 demo application.
+#
+
+menu "WiFi Echo Demo"
+
+    choice
+        prompt "Device Type"
+        default DEVICE_TYPE_ESP32_DEVKITC
+        help
+            Specifies the type of ESP32 device.
+
+            Note that the "ESP32-DevKitC" choice is compatible with a number of clone devices
+            available from third-party manufacturers.
+
+        config DEVICE_TYPE_ESP32_DEVKITC
+            bool "ESP32-DevKitC"
+        config DEVICE_TYPE_M5STACK
+            bool "M5Stack"
+    endchoice
+
+    config ECHO_IPV4
+        bool "IPV4"
+        default y
+
+    config ECHO_IPV6
+        bool "IPV6"
+        default n
+        select EXAMPLE_CONNECT_IPV6
+
+    config ECHO_PORT
+        int "Port"
+        range 0 65535
+        default 8000
+        help
+            Local port the example server will listen on.
+
+endmenu