NDN-JS: A JavaScript client library for Named Data Networking

NDN-JS is the first native version of the NDN protocol written in JavaScript. It implements the NDN packet format.

The project is managed by the UCLA NDN team - for more information on NDN, see https://named-data.net/

See the file INSTALL for build and install instructions.

If you are new to the NDN community of software generally, read the Contributor's Guide. Proposed code contributions should use a GitHub pull request.

License

This program is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with this program. If not, see http://www.gnu.org/licenses/. A copy of the GNU Lesser General Public License is in the file COPYING.

Overview

This is a young project, with minimal documentation that we are slowly enhancing. Please submit any bugs or issues to the NDN-JS issue tracker: https://redmine.named-data.net/projects/ndn-js/issues

The primary goal of NDN-JS is to provide a pure JavaScript implementation of the NDN API that enables developers to create browser-based or Node.js-based applications using Named Data Networking. The approach requires no native code or signed Java applets, and thus can be delivered over the current web to modern browsers with no hassle for the end user.

Additional goals for the project:

• WebSockets transport for the browser (rather than TCP or UDP, which are not directly supported in the browser).
• Relatively lightweight and compact, to enable efficient use on the web.

The library currently requires a remote NDN forwarder, and has been tested with NFD from the package https://github.com/named-data/NFD .

Currently, the library has two APIs for developers:

1. The Javascript API for asynchronous Interest/Data exchange which follows the NDN Common Client Libraries API: https://named-data.net/doc/ndn-ccl-api/ . This API can be used from the browser or Node.js. The browser version uses WebSockets for transport. Node.js can use TCP or Unix sockets.

2. A Firefox plug-in, which implements an "ndn:/" url scheme following NDNFS conventions for file retrieval.

By default, both parts of the library connect automatically to a set of hubs that are part of the NDN research project's testbed. There are currently no restrictions on non-commercial, research-oriented data exchange on this testbed. (Contact [email protected] for more details.) The developer can also specify a local or remote NDN forwarder as well, as an argument to the Face constructor.

JAVASCRIPT API

See files in js/ and examples in tests/, examples/.

NDN-JS currently supports expressing Interests (and receiving data) and publishing Data (that answers Interests). This includes encoding and decoding data packets as well as signing and verifying them using RSA/EC keys.

NDN connectivity

The only way (for now) to get connectivity to other NDN nodes is via an NDN forwarder. JavaScript API in the browser requires NFD's WebSockets transport. Node.js API can use TCP (remote or local) or Unix sockets (to the local NDN forwarder).

Including the scripts on a web page

To use NDN-JS in a web page, one of two scripts must be included using a script tag: ndn.js is a combined library; ndn.min.js is a compressed version of the combined library that loads faster but doesn't show the original source for debugging.

A web page script tag can load a released version from jsDelivr. This URL loads version v0.17.0:

• https://cdn.jsdelivr.net/gh/named-data/[email protected]/build/ndn.min.js

For development, see INSTALL for instructions on how to build these files. Or the latest development snapshot can be downloaded from the build directory:

• https://github.com/named-data/ndn-js/raw/master/build/ndn.js
• https://github.com/named-data/ndn-js/raw/master/build/ndn.min.js

Examples

ndnping

You can check out examples/ndnping/ndn-ping.html to see how to implement ndnping in NDN.js

Example to retrieve content

A simple example of the current API to express an Interest and receive data:

var face = new Face();	// connect to a default hub

function onData(interest, data) {
  console.log("Received " + data.getName().toUri());
}

face.expressInterest(new Name("/ndn/edu/ucla/remap/ndn-js-test/hello.txt"), onData);

Example to publish content

Publishing content requires knowledge of a routable prefix for your upstream NDN forwarder. We are working on a way to either obtain that prefix or use the /local convention. For now, see examples/browser/test-publish-async-nfd.html.

FIREFOX ADD-ON FOR THE NDN PROTOCOL

See files in ndn-protocol/.

NDN-JS includes a Firefox extension for the ndn protocol built with the JavaScript library. It currently obtains NDN connectivity through the NDN testbed, but you can click "Set" on the NDN Toolbar to change the connected hub.

To install, either download https://github.com/named-data/ndn-js/raw/master/ndn-protocol.xpi or use ndn-protocol.xpi in the distribution. In Firefox, open Tools > Add-ons. In the "gear" or "wrench" menu, click Install Add-on From File and open ndn-protocol.xpi. (In Firefox for Android, type file: in the address bar and click the downloaded ndn-protocol.xpi.) Restart Firefox.

Firefox uses the protocol extension to load any URI starting with ndn. See this test page for examples: ndn:/ndn/edu/ucla/remap/demo/ndn-js-test/NDN-Protocol-Examples.html?ndn.ChildSelector=1

When the page is loaded, Firefox updates the address bar with the full matched name from the retrieved content object including the version, but without the implicit digest or segment number (see below).

Interest selectors in the ndn protocol

You can add interest selectors. For example, this uses 1 to select the "rightmost" child (latest version): ndn:/ndn/edu/ucla/remap/ndn-js-test/howdy.txt?my=query&ndn.ChildSelector=1&key=value#ref

The browser loads the latest version and changes the address to: ndn:/ndn/edu/ucla/remap/ndn-js-test/howdy.txt/%FD%052%A1%EA_%89?my=query&key=value#ref

The child selector was used and removed. Note that the other non-ndn query and ref "?key=value#ref" are still present, in case they are needed by the web application.

The following selector keys are supported:

• ndn.MinSuffixComponent= non-negative int
• ndn.MaxSuffixComponents= non-negative int
• ndn.ChildSelector= non-negative int
• ndn.Scope= non-negative int
• ndn.InterestLifetime= non-negative int (milliseconds)
• ndn.PublisherPublicKeyDigest= % escaped value
• ndn.Nonce= % escaped value
• ndn.Exclude= comma-separated list of % escaped values or * for ANY

Multiple segments in the ndn protocol

A URI for content with multiple segments is handled as follows. If the URI has a segment number, just retrieve that segment and return the content to the browser.

Otherwise look at the name in the returned ContentObject. If the returned name has no segment number, just return the content to the browser. If the name has a segment number which isn't 0, store it and express an interest for segment 0. Also express an interest for the highest segment to try to determine the FinalBlockID early. Fetch multiple segments in order and return each content to the browser (in order) as the arrive until we get the segment for FinalBlockID.