webthing
Implementation of an HTTP Web Thing.
Using
If you're using Cargo
, just add webthing
to your Cargo.toml
:
[]
= "0.14"
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.
- Setting this property via a
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:
let mut light = new;
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.
;
let on_description = json!;
let on_description = on_description.as_object.unwrap.clone;
thing.add_property;
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.
;
let brightness_description = json!;
let brightness_description = brightness_description.as_object.unwrap.clone;
thing.add_property;
Now we can add our newly created thing to the server and start it:
let mut things: = Vec new;
things.push
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:
let mut thing = new;
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.
let level_description = json!; let level_description = level_description.as_object.unwrap.clone; thing.add_property;
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.
let sensor = new );
let cloned = sensor.clone;
spawn;
This will update our property with random sensor readings. The new property value is then sent to all websocket listeners.
Adding to Gateway
To add your web thing to the WebThings Gateway, install the "Web Thing" add-on and follow the instructions here.