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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

Default CI Pipeline

Table of Contents

License

Dual-licensed under both

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

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

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 10+ (e.g., 10.13.0 LTS)

Linux

Meet the node-gyp requirements:

  • Python v2.7, v3.5, 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 install the node-wot CLI, either globally (npm i @node-wot/cli -g) or as a (dev) dependency (npm i @node-wot/cli --save or npm i @node-wot/cli --save-dev).

Then, you don't need to specify any further node-wot dependencies and can implement your application (e.g., main.js) without explicitly requiring node-wot dependencies:

//No need to require node-wot componets
// WoT runtime is provided as global object

WoT.produce({/*.....*/})

If the CLI is globally installed, you don't need to set up a Node.js project. If you do so, anyway, you can specify the entry point as follows:

"scripts":{
   "start": "wot-servient main.js"
}

There are several ways to start the application:
a. Execute npm start.
b. Execute ./node_modules/.bin/wot-servient main.js.
c. Execute node ./node_modules/@node-wot/cli/dist/cli.js main.js.
d. If you have installed @node-wot/cli globally you can even start the application right away using this command wot-servient main.js. However, in the current implementation, the import of local dependencies is not supported in this case.

wot-servient can execute multiple files at once, for example as follows:

wot-servient script1.js ./src/script2.js

Finally, to debug use the option --inspect or --inspect-brk if you want to hang until your debug client is connected. Then start Chrome Dev Tools or vscode debugger or your preferred v8 inspector to debug your code.

For further details check: wot-servient --help

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 and lerna):

npm install 

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):

  • yarn init
  • yarn add [packages]
  • npm run build
  • lerna init
  • lerna exec 'npm prune --production'

Trouble shooting

  • Build error around node-aead-crypto
    • node-gyp has been seen failing on MacOS
    • try node 10+, which does not require the crypto polyfill
  • 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 Node 12.13.0

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 --clientonly examples\scripts\counter-client.js

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

How to use the library

The API

This library implements the WoT Scripting API:

You can also see examples/scripts to have a feeling of how to script a Thing.

Logging

We used to have a node-wot-logger package to allow fine-grained logging (by means of Winston). It turned out though that depending on the actual use-case other logging libraries might be better suited. Hence we do not want to prescribe which logging library to use. Having said that, we use console statements which can be easily overriden to use the prefered logging library if needed (see here).

The logs in the library follows those best practice rules (see here):

  1. Tag log messages with the package as following: console.debug("[package-name]", "log message). This is useful to identify which package generated the log.
  2. Avoid to use info and log in packages other than the cli package.

Please follows these rules if you are going to contribute to node-wot library.

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