# multicast-dns Low level multicast-dns implementation in pure javascript ``` npm install multicast-dns ``` [![build status](http://img.shields.io/travis/mafintosh/multicast-dns.svg?style=flat)](http://travis-ci.org/mafintosh/multicast-dns) ## Usage ``` js var mdns = require('multicast-dns')() 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 'brunhilde.local' mdns.query({ questions:[{ name: 'brunhilde.local', type: 'A' }] }) ``` Running the above (change `brunhilde.local` to `your-own-hostname.local`) will print an echo of the query packet first ``` js got a query packet: { type: 'query', questions: [ { name: 'brunhilde.local', type: 'A', class: 1 } ], answers: [], authorities: [], additionals: [] } ``` And then a response packet ``` js got a response packet: { type: 'response', questions: [], answers: [ { name: 'brunhilde.local', type: 'A', class: 'IN', ttl: 120, flush: true, data: '192.168.1.5' } ], authorities: [], additionals: [ { name: 'brunhilde.local', type: 'A', class: 'IN', ttl: 120, flush: true, data: '192.168.1.5' }, { name: 'brunhilde.local', type: 'AAAA', class: 'IN', ttl: 120, flush: true, data: 'fe80::5ef9:38ff:fe8c:ceaa' } ] } ``` # CLI ``` npm install -g multicast-dns ``` ``` multicast-dns brunhilde.local > 192.168.1.1 ``` # API A packet has the following format ``` js { questions: [{ name: 'brunhilde.local', type: 'A' }], answers: [{ name: 'brunhilde.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 ``` js { 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. ``` js mdns.on('query', function(query) { if (query.questions[0] && query.questions[0].name === 'brunhilde.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 ``` js mdns.query('brunhilde.local', 'A') mdns.query([{name:'brunhilde.local', type:'A'}]) mdns.query({ questions: [{name:'brunhilde.local', type:'A'}] }) ``` #### `mdns.respond(packet, [cb])` Send a dns response. The callback will be called when the packet was sent. ``` js // reply with a SRV and a A record as an answer mdns.respond({ answers: [{ name: 'my-service', type: 'SRV', data: { port: 9999, weight: 0, priority: 10, target: 'my-service.example.com' } }, { name: 'brunhilde.local', type: 'A', ttl: 300, data: '192.168.1.5' }] }) ``` The following shorthands are equivalent ``` js mdns.respond([{name:'brunhilde.local', type:'A', data:'192.158.1.5'}]) mdns.respond({ answers: [{name:'brunhilde.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/mafintosh/multicast-dns.git npm install node example.js node cli.js $(hostname).local ``` ## License MIT