A simple server for the ESP8266, the ESP32, boards with Ethernet, or any WiFi101-compatible board that implements Mozilla's proposed Web of Things API. The LED example exposes an OnOffSwitch named "Built-in LED" which controls the board's built-in LED. The LED Lamp example ups the ante by introducing a level property to expose a dimmable Light.

To run on either of these boards, download the Arduino IDE and set it up for board-specific development. These Adafruit guides explain how to set up for an ESP8266 and how to set up for an ESP32. You will also need to download the ESP Async WebServer library and unpack it in your sketchbook's libraries folder.

• MKR1000 (and similar): Install the WiFi101 library from the Arduino library manager.
• MKR1010 (and similar): Install the WiFiNINA library from the Arduino library manager.

Make sure to install the current release of the ArduinoJson library (6) if you don't have it installed already.

Next, download this library from the same library manager by searching for webthing.

You should be able to upload the example sketch onto your board and use it as a simple Web Thing. This Web Thing can be talked to using the WoT API or added to the WebThings Gateway using the "Add Thing by URL" feature. Note that right now, WiFi101-based Things must be manually added by typing the full URL to the Web Thing, e.g. http://192.168.0.103/things/led.

If you want to create a Web Thing from scratch, make sure to include both "Thing.h" and "WebThingAdapter.h" (or "EthernetWebThingAdapter.h", if using an Ethernet board). You can then add Things and Properties to your board using our proposed API.

Add the webthing-arduino library through PlatformIO's package management interface. Ensure that you get the latest release by examining the entries in the version number dropdown list. It may be sorted counter-intuitively. You may also need to manually add the ArduinoJson and other libraries to your project.

#include <Arduino.h>
#include "Thing.h"
#include "WebThingAdapter.h"

// TODO: Hardcode your wifi credentials here (and keep it private)
const char *ssid = "public";
const char *password = "";

#if defined(LED_BUILTIN)
const int ledPin = LED_BUILTIN;
#else
const int ledPin = 13; // manually configure LED pin
#endif

WebThingAdapter *adapter;

const char *ledTypes[] = {"OnOffSwitch", "Light", nullptr};
ThingDevice led("led", "Built-in LED", ledTypes);
ThingProperty ledOn("on", "", BOOLEAN, "OnOffProperty");

bool lastOn = false;

void setup(void) {
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, HIGH);
  Serial.begin(115200);
  Serial.println("");
  Serial.print("Connecting to \"");
  Serial.print(ssid);
  Serial.println("\"");
#if defined(ESP8266) || defined(ESP32)
  WiFi.mode(WIFI_STA);
#endif
  WiFi.begin(ssid, password);
  Serial.println("");

  // Wait for connection
  bool blink = true;
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
    digitalWrite(ledPin, blink ? LOW : HIGH); // active low led
    blink = !blink;
  }
  digitalWrite(ledPin, HIGH); // active low led

  Serial.println("");
  Serial.print("Connected to ");
  Serial.println(ssid);
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
  adapter = new WebThingAdapter("w25", WiFi.localIP());

  led.addProperty(&ledOn);
  adapter->addDevice(&led);
  adapter->begin();
  Serial.println("HTTP server started");
  Serial.print("http://");
  Serial.print(WiFi.localIP());
  Serial.print("/things/");
  Serial.println(led.id);
}

void loop(void) {
  adapter->update();
  bool on = ledOn.getValue().boolean;
  digitalWrite(ledPin, on ? LOW : HIGH); // active low led
  if (on != lastOn) {
    Serial.print(led.id);
    Serial.print(": ");
    Serial.println(on);
  }
  lastOn = on;
}

• If you have a complex device with large thing descriptions, you may need to increase the size of the JSON buffers. The buffer sizes are configurable as such:

  // By default, buffers are 256 bytes for small documents, 1024 for larger ones
  
  // To use a pre-defined set of larger JSON buffers (4x larger)
  #define LARGE_JSON_BUFFERS 1
  
  // Else, you can define your own size
  #define SMALL_JSON_DOCUMENT_SIZE <something>
  #define LARGE_JSON_DOCUMENT_SIZE <something>
  
  #include <Thing.h>
  #include <WebThingAdapter.h>

To add your web thing to the WebThings Gateway, install the "Web Thing" add-on and follow the instructions here.