CoAP Protocol Binding of node-wot

W3C WoT Binding Template specification for CoAP can be found here.

Current Maintainer(s): @JKRhb

Protocol specifier

The protocol prefix handled by this binding is coap:// or coaps://.

Getting Started

In the following examples, how to use the CoAP binding of node-wot is shown.

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- npm install @node-wot/core
- npm install @node-wot/binding-coap

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The client example tries to connect to a TestThing via CoAP and read the string property.
The Thing Description is located under the following CoAP URI coap://plugfest.thingweb.io:5683/testthing.

node example-client.js

``js
// example-client.js
const { Servient } = require("@node-wot/core");
const { CoapClientFactory } = require("@node-wot/binding-coap");

// create Servient and add CoAP binding
const servient = new Servient();
servient.addClientFactory(new CoapClientFactory());

servient
.start()
.then(async (WoT) => {
try {
const td = await WoT.requestThingDescription("coap://plugfest.thingweb.io:5683/testthing");
const thing = await WoT.consume(td);

// read property
const read1 = await thing.readProperty("string");
console.log("string value is: ", await read1.value());
} catch (err) {
console.error("Script error:", err);
}
})
.catch((err) => {
console.error("Start error:", err);
});
`

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The server example produces a thing that allows for setting a property count. The thing is reachable through CoAP.

node example-server.js

`js
// example-server.js
const { Servient } = require("@node-wot/core");
const { CoapServer } = require("@node-wot/binding-coap");

// create Servient add HTTP binding
const servient = new Servient();
servient.addServer(new CoapServer());

servient.start().then((WoT) => {
WoT.produce({
title: "MyCounter",
properties: {
count: {
type: "integer",
},
},
}).then((thing) => {
console.log("Produced " + thing.getThingDescription().title);

let count = 0;

// set property handlers (using async-await)
thing.setPropertyReadHandler("count", async () => count);
thing.setPropertyWriteHandler("count", async (intOutput) => {
count = await intOutput.value();
});

thing.expose().then(() => {
console.info(thing.getThingDescription().title + " ready");
console.info("TD : " + JSON.stringify(thing.getThingDescription()));
});
});
});
``

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See