num-client

NUM Client

A TypeScript/JavaScript client for the NUM protocol.

See the full Specification at the NUM Protocol Website and the Explainer for more information.

The NUM protocol supports a range of modules that add rich functionality in an extensible way.

The NUM URI Scheme

The NUM protocol uses the familiar URL format for its URIs and allows modules to interpret data in a variety of ways.

The data stored in a NUM Record is converted to JSON String format that can be parsed into JSON objects for straightforward incorporation into TypeScript and JavaScript programs. Here are some example NUM URIs with module 1 - the Contacts module. The default module is 0 (zero) if no module is specified, which has no module schema.

• num://numexample.com:1
• num://[e-mail]:1
• num://[e-mail]:1/work
• num://[e-mail]:1/personal
• num://[e-mail]:1/hobbies
• num://numexample.com:1/support
• num://numexample.com:1/support/website
• num://numexample.com:1/support/delivery
• num://numexample.com:1/enquiries
• num://numexample.com:1/sales

As you can see from the examples above, data can be associated with domains and email addresses, and can be organised hierarchically if desired. In future, the protocol will support more than just domains and email addresses.

Additional modules can be referenced in the same way as ports in other URIs:

• num://numexample.com:2 for the Registrant module.
• num://numexample.com:3 for the Images module.
• num://numexample.com:4 for the Custodians module.
• num://numexample.com:5 for the Payments module.
• num://numexample.com:6 for the Regulatory module.
• num://numexample.com:7 for the Public Key module.
• num://numexample.com:8 for the Intellectual Property module.
• num://numexample.com:9 for the Terms module.
• num://numexample.com:10 for the Bugs module.
• num://numexample.com:nn for your own module?

Adding Support for the NUM Protocol

Install using:

npm install -s num-client

TypeScript Examples

Importing the Client

Use this import to make the client available for use:

import { 
  createClient,     // required for creating the `NUMClient`
  createDnsClient,  // optional unless you need to override the default DoH endpoint
  parseNumUri,      // required for converting the NUM URI string into a valid `NumUri` object
  CallbackHandler,  // optional unless you need to provide a custom callback handler implementation
  DoHResolver,      // optional unless you need to override the default DoH endpoint
  Location          // optional unless you need to provide a custom callback handler implementation
} from 'num-client';

The Simplest Usage

The programming interface is very simple:

const lookup = async () => {
  const numUri = parseNumUri('num.uk:1');             // Parse the NUM URI
  const client = createClient();                      // Create a NumClient
  const ctx = client.createContext(numUri);           // Set the lookup context
  const result = await client.retrieveNumRecord(ctx); // Use the context to retrieve a NUM record
  console.log(result);                                // Handle the result
}

Reusing the NUMClient

The same NUMClient can be reused for multiple lookups, as in this example:

const lookup = async () => {
  const numUri1 = parseNumUri('num.uk:1');
  const numUri2 = parseNumUri('numexample.com:1');

  const client = createClient();            // This client is reused for multiple contexts

  const ctx1 = client.createContext(numUri1);
  const ctx2 = client.createContext(numUri2);

  const result1 = client.retrieveNumRecord(ctx1);
  const result2 = client.retrieveNumRecord(ctx2);

  const result = await Promise.all([result1, result2]);

  console.log(result[0]);
  console.log(result[1]);
}

Overriding the Default DoH Endpoint

By default the NUMClient uses the Google DoH resolver, although it can be changed if required by providing a DoHResolver to a service that supports the JSON API for DNS over HTTPS (DoH).:

const lookup = async () => {
  // ...
  const DEFAULT_RESOLVER = new DoHResolver('Google', 'https://dns.google.com/resolve');
  const dnsClient = createDnsClient(DEFAULT_RESOLVER);

  const client = createClient(dnsClient); // Use a custom DoH service
  // ...
};

Providing User Variable Values

Some modules can be provided with User Variable values to customise the output, as in this example:

const lookup = async () => {
  const numUri = parseNumUri('num.uk:1');             // Parse the NUM URI
  const client = createClient();                      // Create a NumClient
  const ctx = client.createContext(numUri);           // Set the lookup context

  ctx.setUserVariable('_L', 'en');                    // Set the user's language
  ctx.setUserVariable('_C', 'gb');                    // Set the user's country

  const result = await client.retrieveNumRecord(ctx); // Use the context to retrieve a NUM record
  console.log(result)                                 // Handle the result
}

Using a CallbackHandler

Lookups can take several seconds, so you can provide a CallbackHandler rather than awaiting the results:

const lookup = async () => {
  const numUri = parseNumUri('num.uk:1');             // Parse the NUM URI
  const client = createClient();                      // Create a NumClient
  const ctx = client.createContext(numUri);           // Set the lookup context

  const handler: CallbackHandler = {                  // Provide a custom CallbackHandler
    setLocation: (l: Location): void => {
      console.log(l);                                 // `l` is the `Location` where the result was found
    },
    setResult: (r: string): void => {
      console.log(r);                                 // `r` is the NUM record as a JSON string
    },
  };

  client.retrieveNumRecord(ctx, handler).then((_r) => {
    // Ignore because the callback handler will handle it
  });
}

JavaScript Examples

The Simplest Usage

This example shows the minimal requirements for using the NUM Client:

const num = require('num-client');

function lookup(uri) {
  const numUri = num.parseNumUri(uri);

  const client = num.createClient();
  const ctx = client.createContext(numUri);

  return client.retrieveNumRecord(ctx);
}

lookup('num.uk:1').then((result) => console.log(result));

Full Usage

This example shows how to use all features of the client, including

• overriding the DoH resolver,
• reusing the NUMClient
• setting user variables
• using a callback handler

const num = require('num-client');

function lookup(uri1, uri2) {
  const numUri1 = num.parseNumUri(uri1);
  const numUri2 = num.parseNumUri(uri2);

  const DEFAULT_RESOLVER = new num.DoHResolver('Google', 'https://dns.google.com/resolve');
  const dnsClient = num.createDnsClient(DEFAULT_RESOLVER);

  const client = num.createClient(dnsClient);          // Use a custom DNS client

  const ctx1 = client.createContext(numUri1);
  const ctx2 = client.createContext(numUri2);

  ctx1.setUserVariable('_L', 'en');                    // Set the user's language
  ctx1.setUserVariable('_C', 'gb');                    // Set the user's country

  ctx2.setUserVariable('_L', 'en');                    // Set the user's language
  ctx2.setUserVariable('_C', 'us');                    // Set the user's country

  const handler = {                                    // Provide a custom CallbackHandler
    setLocation: (l) => {
      console.log(l);                                  // `l` is the `Location` where the result was found
    },
    setResult: (r) => {
      console.log(r);                                 // `r` is the NUM record as a JSON string
    },
  };

  const result1 = client.retrieveNumRecord(ctx1, handler);
  const result2 = client.retrieveNumRecord(ctx2, handler);

  return Promise.all([result1, result2]);
}

lookup('num.uk:1', 'numexample.com:1').then((result) => {
  // Ignore because the callback handler will handle the results.
});