Eclipse Thingweb node-wot

W3C Web of Things implementation on NodeJS.

Visit http://www.thingweb.io for a practical node-wot API usage, hands-on tutorials or additional information.

Useful labels: question | good first issue

Table of Contents

• License
• Implemented/supported features
  • Protocol Support
  • MediaType Support
• Prerequisites
  • To use with Node.js
  • To use in a browser
• How to get the library
  • As a Node.js dependency
  • As a standalone application
  • As a Docker image
  • As a browser library
• No time for explanations - show me a running example!
  • Using Node.js
  • Using Docker
  • Using a browser
  • Online Things
• How to use the library
  • The API
  • TD Tooling
  • Logging
  • Install new/different versions of NodeJS

License

Dual-licensed under both

• Eclipse Public License v. 2.0
• W3C Software Notice and Document License (2015-05-13)

Pick one of these two licenses that fits your needs. Please also see the additional notices and how to contribute.

Implemented/supported features

Protocol Support

• HTTP ✔️
• HTTPS ✔️
• CoAP ✔️
• CoAPS ✔️
• MQTT ✔️
• Firestore ✔️
• Websocket ➕ (Server only)
• OPC-UA ➕ (Client only)
• NETCONF ➕ (Client only)
• Modbus ➕ (Client only)
• M-Bus ➕ (Client only)

Note: More protocols can be easily added by implementing ProtocolClient, ProtocolClientFactory, and ProtocolServer interface.

Note: the bindings for binding-fujitsu and binding-oracle were removed after v0.7.x due to lack of maintainers.

MediaType Support

• JSON ✔️
• Text (HTML, CSS, XML, SVG) ✔️
• Base64 (PNG, JPEG, GIF) ✔️
• Octet stream ✔️
• CBOR ✔️
• EXI ⏲️

Note: More mediaTypes can be easily added by implementing ContentCodec interface.

const ContentSerdes = require('@node-wot/core').ContentSerdes
const JsonCodec = require('@node-wot/core').JsonCodec

// e.g., assign built-in codec for *new* contentType
let cs = ContentSerdes.get();
cs.addCodec(new JsonCodec("application/calendar+json"));

// e.g., assign *own* MyCodec implementation (implementing ContentCodec interface)
cs.addCodec(new MyCodec("application/myType"));

Prerequisites

To use with Node.js

All systems require:

• NodeJS version 14+
• npm version 7+

Linux

Meet the node-gyp requirements:

• Python v3.6, v3.7, or v3.8
• make
• A proper C/C++ compiler toolchain, like GCC

Windows

Install the Windows build tools through a CMD shell as administrator:

npm install -g --production windows-build-tools

WSL: Windows Services for Linux should follow Linux instructions.

Mac OS

Meet the node-gyp requirements:

xcode-select --install

To use in a browser

To use node-wot as a browser-side JavaScript Library, the browser needs to support ECMAScript 2015. Supported browsers include:

• Microsoft Edge 15 and later
• Firefox 54 and later
• Chrome 58 and later
• Safari 10 and later

Using a browser with only ES5 support (eg. IE 11) might be possible if you add polyfills.

How to get the library

As a Node.js dependency

You can install node-wot in the following ways:

1. As a normal dependency (i.e., like loadsh). In this case, you are embedding a servient inside your application.
2. As a CLI to run scripts. In this case, your application is running inside the default servient.

Normal Dependency

If you want to use node-wot as a library in your Node.js application, you can use npm to install the node-wot packages that you need. To do so, cd inside you application folder, and run:

npm i @node-wot/core @node-wot/binding-http --save

Now, you can implement a thing as follows:

// server.js
// Required steps to create a servient for creating a thing
const Servient = require('@node-wot/core').Servient;
const HttpServer = require('@node-wot/binding-http').HttpServer;

const servient = new Servient();
servient.addServer(new HttpServer());

servient.start().then((WoT) => {
    // Then from here on you can use the WoT object to produce the thing
    // i.e WoT.produce({.....})
});

A client consuming a thing can be implemented like this:

// client.js
// Required steps to create a servient for a client
const { Servient, Helpers } = require("@node-wot/core");
const { HttpClientFactory } = require('@node-wot/binding-http');

const servient = new Servient();
servient.addClientFactory(new HttpClientFactory(null));
const WoTHelpers = new Helpers(servient);

WoTHelpers.fetch("http://localhost:8080/example").then(async (td) => {
    try {
        servient.start().then(async (WoT) => {
            // Then from here on you can consume the thing
            // i.e let thing = await WoT.consume(td) ...
        });
    }
    catch (err) {
        console.error("Script error:", err);
    }
}).catch((err) => { console.error("Fetch error:", err); });

You can then start the applications with node by running node server.js and node client.js.

CLI Tool

You can alternatively use node-wot via its command line interface (CLI). Please visit the CLI tool's Readme to find out more.

As a standalone application

Clone and build

Clone the repository:

git clone https://github.com/eclipse-thingweb/node-wot

Go into the repository:

cd thingweb.node-wot

Install root dependencies (locally installs tools such as typescript):

npm ci

Use tsc to transcompile TS code to JS in dist directory for each package: Note: This step automatically calls npm run bootstrap.

npm run build

Optional steps

Link Packages

Make all packages available on your local machine (as symlinks). You can then use each package in its local version via npm link <module> instead of npm install <module> (see also https://docs.npmjs.com/cli/link).

sudo npm run link

(On Windows omit sudo)

Link Local wot-typescript-definitions

To evolve the Scripting API in development, you need to use a locally changed version of the wot-typescript-definitions. Use npm link for this as well:

git clone https://github.com/w3c/wot-scripting-api/
cd wot-scripting-api/typescript/
sudo npm link

(On Windows omit sudo)

In each node-wot package, link the local version made available in the previous step:

sudo npm link wot-typescript-definitions

(On Windows omit sudo)

Optimization

To reduce the size of the installation from about 800 MByte down to about 200 MByte, you can run the following commands (currently only tested on Linux): npm prune --production

Trouble shooting

• Build error about No matching version found for @node-wot/... or something about match
  • try npm run unlock from project root before building
• sudo npm run link does not work
  • try npm run unlock from project root before calling [sudo] npm run link
  • try npm link in each package directory in this order: td-tools, core, binding-*, cli, demo-servients
• Error mesage for npm link @node-wot/<module> ELOOP: too many symbolic links encountered, stat '/usr/lib/node_modules/@node-wot/<module>
  1. Run npm run link in thingweb.node-wot again
  2. Remove node_modules in the targeted project
  3. Remove all @node-wot/<module> dependencies in your package.json
  4. Run npm i again
  5. Install the packages with npm link @node-wot/<module>
• Build error around prebuild: npm run bootstrap
  • This has been seen failing on WSL. Try using a more recent NodeJS version

As a Docker image

Alternatively, node-wot can be built as a Docker image with the Dockerfile.

Make sure you are under linux or under WSL if you are running on Windows.

Clone the repository:

git clone https://github.com/eclipse-thingweb/node-wot

Go into the repository:

cd thingweb.node-wot

Build the Docker image named wot-servient from the Dockerfile:

npm run build:docker

Run the wot-servient as a container:

docker run --rm wot-servient -h

As a browser library

node-wot can also be imported as browser-side library. To do so, include the following script tag in your html:

<script src="https://cdn.jsdelivr.net/npm/@node-wot/browser-bundle@latest/dist/wot-bundle.min.js"></script>

In the browser, node wot only works in client mode with limited binding support. Supported bindings: HTTP / HTTPS / WebSockets You can access all node-wot functionality through the "Wot" global object:

var servient = new Wot.Core.Servient();
var client = new Wot.Http.HttpClient();

No time for explanations - show me a running example!

Using Node.js

Run all the steps above including "Link Packages" and then run this:

wot-servient -h
cd examples/scripts
wot-servient

Without the "Link Packages" step, the wot-servient command is not available and node needs to be used (e.g., Windows CMD shell):

# expose
node packages\cli\dist\cli.js examples\scripts\counter.js
# consume
node packages\cli\dist\cli.js --client-only examples\scripts\counter-client.js

• Go to http://localhost:8080/counter and you'll find a thing description
• Query the count by http://localhost:8080/counter/properties/count
• Modify the count via POST on http://localhost:8080/counter/actions/increment and http://localhost:8080/counter/actions/decrement
• Application logic is in examples/scripts/counter.js

Using Docker

First build the docker image and then run the counter example:

# expose
docker run -it --init -p 8080:8080/tcp -p 5683:5683/udp -v "$(pwd)"/examples:/srv/examples --rm wot-servient /srv/examples/scripts/counter.js
# consume
docker run -it --init -v "$(pwd)"/examples:/srv/examples --rm --net=host wot-servient /srv/examples/scripts/counter-client.js --client-only

• The counter exposes the HTTP endpoint at 8080/tcp and the CoAP endpoint at 5683/udp and they are bound to the host machine (with -p 8080:8080/tcp -p 5683:5683/udp).
• The counter-client binds the network of the host machine (--net=host) so that it can access the counter thing's endpoints.
• --init allows the containers to be killed with SIGINT (e.g., Ctrl+c)
• -v "$(pwd)"/examples:/srv/examples mounts the examples directory to /srv/examples on the container so that the node inside the container can read the example scripts.

Using a browser

An example of how to use node-wot as a browser-side library can be found under examples/browser/index.html. To run it, open examples/browser/index.html in a modern browser, and consume the test Thing available under http://plugfest.thingweb.io:8083/testthing to interact with it.

The JavaScript code that uses node-wot as a library to power this application can be found under: examples/browser/index.js

Online Things

We offer online simulated Things that are available to be used by anyone.

Their TDs are available at the following links:

• Counter: HTTP at http://plugfest.thingweb.io:8083/counter and CoAP at coap://plugfest.thingweb.io:5683/counter
• Smart Coffee Machine: HTTP at http://plugfest.thingweb.io:8083/smart-coffee-machine and CoAP at coap://plugfest.thingweb.io:5683/smart-coffee-machine
• TestThing: HTTP at http://plugfest.thingweb.io:8083/testthing and CoAP at coap://plugfest.thingweb.io:5683/testthing

All of them require no security mechanism to be communicated with and have same behavior from CoAP or HTTP endpoints. Below are small explanations on what they can be used for:

• Counter: It has a count property that can be read or observed and can be incremented or decremented via separate actions. It is also possible to reset the count the value, obtain when the last change occured, subscribe to a change in the count value or get the count value as an image.
• TestThing: This Thing exists primarily for testing different data schemas and payload formats. It also has events attached to affordances that notify when a value changes.
• Smart Coffee Machine: This is a simulation of a coffee machine that also has a simple user interface that displays the values of properties. In addition to proving a real life device example, it can be used for testing uriVariables. You can ask it to brew different coffees and monitor the available resource level.

How to use the library

The API

This library implements the WoT Scripting API:

• Editors Draft in master
• Working Draft corresponding to node-wot release versions

Additionally, you can have a look at our API Documentation.

To learn by examples, see examples/scripts to have a feeling of how to script a Thing or a Consumer.

TD Tooling

The package td-tools provides utilties around ThingDescription (TD) tooling:

• ThingDescription (TD) parsing
• ThingModel (TM) tooling
• Asset Interface Description (AID) utility
• ...

Logging

Logging in node-wot is implemented via the debug package. This allows users to enable log messages for specific logging levels (info, debug, warn, or error) or packages. Which log messages are emitted is controlled by the DEBUG environment variable.

In the following, we will show a couple of examples for its usage using wildcard characters (*). Note, however, that the syntax for setting an environment variable depends on your operating system and the terminal you use. See the debug documentation for more details on platform-specific differences.

First, you can enable all log messages by setting DEBUG to a wildcard like so:

DEBUG=* npm start

To only show node-wot-specific logging messages, prefix the wildcard with node-wot:

DEBUG=node-wot* npm start

To only show a specific log level, use one of info, debug, warn, or error as the suffix. Note in this context that you can provide multiple values for DEBUG. For example, if you want to show only debug and info messages, you can use the following:

DEBUG='*debug,*info' npm start

Finally, you can choose to only display log messages from a specific node-wot package. For example, if you only want to see log messages for the core package, use the following:

DEBUG=node-wot:core* npm start

Using the log levels above, you can also apply more fine-grained parameters for logging. For instance, if you only want to see error messages from the binding-coap package, use this:

DEBUG=node-wot:binding-coap*error npm start

Install new/different versions of NodeJS

Using NPM, you can install NodeJS independent from the usually outdated package managers such as apt. This is nicely done by n:

sudo npm cache clean -f
sudo npm install -g n

To get the "stable" version:

sudo n stable

To get the "latest" version:

sudo n latest

Finally, make the node command available through:

sudo ln -sf /usr/local/n/versions/node/<VERSION>/bin/node /usr/bin/node

Development Internals