webthing

Implementation of an HTTP Web Thing.

Using

If you're using Cargo, just add webthing to your Cargo.toml:

toml [dependencies] webthing = "0.9"

TLS Support

If you need TLS support for the server, you'll need to compile with the ssl feature set.

Example

In this example we will set up a dimmable light and a humidity sensor (both using fake data, of course). Both working examples can be found in here.

Dimmable Light

Imagine you have a dimmable light that you want to expose via the web of things API. The light can be turned on/off and the brightness can be set from 0% to 100%. Besides the name, description, and type, a Light is required to expose two properties: * on: the state of the light, whether it is turned on or off * Setting this property via a PUT {"on": true/false} call to the REST API toggles the light. * brightness: the brightness level of the light from 0-100% * Setting this property via a PUT call to the REST API sets the brightness level of this light.

First we create a new Thing:

rust let mut light = BaseThing::new( "My Lamp".to_owned(), Some(vec!["OnOffSwitch".to_owned(), "Light".to_owned()]), Some("A web connected lamp".to_owned()), );

Now we can add the required properties.

The on property reports and sets the on/off state of the light. For our purposes, we just want to log the new state if the light is switched on/off.

```rust struct OnValueForwarder;

impl ValueForwarder for OnValueForwarder { fn setvalue(&mut self, value: serdejson::Value) -> Result { println!("On-State is now {}", value); Ok(value) } }

let ondescription = json!({ "@type": "OnProperty", "title": "On/Off", "type": "boolean", "description": "Whether the lamp is turned on" }); let ondescription = ondescription.asobject().unwrap().clone(); thing.addproperty(Box::new(BaseProperty::new( "on".toowned(), json!(true), Some(Box::new(OnValueForwarder)), Some(on_description), ))); ```

The brightness property reports the brightness level of the light and sets the level. Like before, instead of actually setting the level of a light, we just log the level.

```rust struct BrightnessValueForwarder;

impl ValueForwarder for BrightnessValueForwarder { fn setvalue(&mut self, value: serdejson::Value) -> Result { println!("Brightness is now {}", value); Ok(value) } }

let brightnessdescription = json!({ "@type": "BrightnessProperty", "title": "Brightness", "type": "number", "description": "The level of light from 0-100", "minimum": 0, "maximum": 100, "unit": "percent" }); let brightnessdescription = brightnessdescription.asobject().unwrap().clone(); thing.addproperty(Box::new(BaseProperty::new( "brightness".toowned(), json!(50), Some(Box::new(BrightnessValueForwarder)), Some(brightness_description), ))); ```

Now we can add our newly created thing to the server and start it:

```rust let mut things: Vec>>> = Vec::new(); things.push(Arc::new(RwLock::new(Box::new(light)));

// If adding more than one thing, use ThingsType::Multiple() with a name. // In the single thing case, the thing's name will be broadcast. let mut server = WebThingServer::new( ThingsType::Multiple(things, "LightAndTempDevice".toowned()), Some(8888), None, Box::new(Generator), ); let serveraddr = server.create(); server.start(); ```

This will start the server, making the light available via the WoT REST API and announcing it as a discoverable resource on your local network via mDNS.

Sensor

Let's now also connect a humidity sensor to the server we set up for our light.

A MultiLevelSensor (a sensor that returns a level instead of just on/off) has one required property (besides the name, type, and optional description): level. We want to monitor this property and get notified if the value changes.

First we create a new Thing:

rust let mut thing = BaseThing::new( "My Humidity Sensor".to_owned(), Some(vec!["MultiLevelSensor".to_owned()]), Some("A web connected humidity sensor".to_owned()), );

Then we create and add the appropriate property: * level: tells us what the sensor is actually reading * Contrary to the light, the value cannot be set via an API call, as it wouldn't make much sense, to SET what a sensor is reading. Therefore, we are creating a readOnly property.

```rust
let level_description = json!({
    "@type": "LevelProperty",
    "title": "Humidity",
    "type": "number",
    "description": "The current humidity in %",
    "minimum": 0,
    "maximum": 100,
    "unit": "percent",
    "readOnly": true
});
let level_description = level_description.as_object().unwrap().clone();
thing.add_property(Box::new(BaseProperty::new(
    "level".to_owned(),
    json!(0),
    None,
    Some(level_description),
)));
```

Now we have a sensor that constantly reports 0%. To make it usable, we need a thread or some kind of input when the sensor has a new reading available. For this purpose we start a thread that queries the physical sensor every few seconds. For our purposes, it just calls a fake method.

```rust let sensor = Arc::new(RwLock::new(Box::new(sensor)))); let cloned = sensor.clone(); thread::spawn(move || { let mut rng = rand::thread_rng();

// Mimic an actual sensor updating its reading every couple seconds.
loop {
    thread::sleep(time::Duration::from_millis(3000));
    let t = cloned.clone();
    let new_value = json!(
        70.0 * rng.gen_range::<f32>(0.0, 1.0) * (-0.5 + rng.gen_range::<f32>(0.0, 1.0))
    );

    {
        let mut t = t.write().unwrap();
        let prop = t.find_property("level".to_owned()).unwrap();
        let _ = prop.set_value(new_value.clone());
    }

    t.write()
        .unwrap()
        .property_notify("level".to_owned(), new_value);
}

}); ```

This will update our property with random sensor readings. The new property value is then sent to all websocket listeners.