dWeb's MultiCast DNS

@distdns/core

dWeb Multicast DNS Javascript Library

npm install @distdns/core

Usage

var mDNS = require('@distdns/core')()

mDNS.on('response', function(response) {
  console.log('got a response packet:', response)
})

mDNS.on('query', function(query) {
  console.log('got a query packet:', query)
})

// lets query for an A record for 'dweb.local'
mDNS.query({
  questions:[{
    name: 'dweb.local',
    type: 'A'
  }]
})

Running the above (change dweb.local to your-own-hostname.local) will print an echo of the query packet first

got a query packet: { type: 'query',
  questions: [ { name: 'dweb.local', type: 'A', class: 1 } ],
  answers: [],
  authorities: [],
  additionals: [] }

And then a response packet

got a response packet: { type: 'response',
  questions: [],
  answers:
   [ { name: 'dweb.local',
       type: 'A',
       class: 'IN',
       ttl: 120,
       flush: true,
       data: '192.168.1.5' } ],
  authorities: [],
  additionals:
   [ { name: 'dweb.local',
       type: 'A',
       class: 'IN',
       ttl: 120,
       flush: true,
       data: '192.168.1.5' },
     { name: 'dweb.local',
       type: 'AAAA',
       class: 'IN',
       ttl: 120,
       flush: true,
       data: 'fe80::5ef9:38ff:fe8c:ceaa' } ] }

CLI

npm install -g @distdns/core

mdns dweb.local
> 192.168.1.1

API

A packet has the following format

{
  questions: [{
    name:'dweb.local',
    type:'A'
  }],
  answers: [{
    name:'dweb.local',
    type:'A',
    ttl:seconds,
    data:(record type specific data)
  }],
  additionals: [
    (same format as answers)
  ],
  authorities: [
    (same format as answers)
  ]
}

Currently data from SRV, A, PTR, TXT, AAAA and HINFO records is passed

mDNS = multicastdns([options])

Creates a new mdns instance. Options can contain the following

{
  multicast: true // use udp multicasting
  interface: '192.168.0.2' // explicitly specify a network interface. defaults to all
  port: 5353, // set the udp port
  ip: '224.0.0.251', // set the udp ip
  ttl: 255, // set the multicast ttl
  loopback: true, // receive your own packets
  reuseAddr: true // set the reuseAddr option when creating the socket (requires node >=0.11.13)
}

mDNS.on('query', (packet, rinfo))

Emitted when a query packet is received.

mdns.on('query', function(query) {
  if (query.questions[0] && query.questions[0].name === 'dweb.local') {
    mdns.respond(someResponse) // see below
  }
})

mDNS.on('response', (packet, rinfo))

Emitted when a response packet is received.

The response might not be a response to a query you send as this is the result of someone multicasting a response.

mDNS.query(packet, [cb])

Send a dns query. The callback will be called when the packet was sent.

The following shorthands are equivalent

mDNS.query('dweb.local', 'A')
mDNS.query([{name:'dweb.local', type:'A'}])
mDNS.query({
  questions: [{name:'dweb.local', type:'A'}]
})

mDNS.respond(packet, [cb])

Send a dns response. The callback will be called when the packet was sent.

// reply with a SRV and a A record as an answer
mDNS.respond({
  answers: [{
    name: 'my-service',
    type: 'SRV',
    data: {
      port:9999,
      weigth: 0,
      priority: 10,
      target: 'my-service.example.com'
    }
  }, {
    name: 'dweb.local',
    type: 'A',
    ttl: 300,
    data: '192.168.1.5'
  }]
})

The following shorthands are equivalent

mDNS.respond([{name:'dweb.local', type:'A', data:'192.158.1.5'}])
mDNS.respond({
  answers: [{name:'dweb.local', type:'A', data:'192.158.1.5'}]
})

mDNS.destroy()

Destroy the mDNS instance. Closes the UDP socket.

Development

To start hacking on this module you can use this example to get started

git clone git://github.com/distdns/core.git
npm install
node example.js
mdns $(hostname).local

License

MIT