mdns-server.js
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'use strict'
var multicastdns = require('multicast-dns')
var dnsEqual = require('dns-equal')
var flatten = require('array-flatten')
var deepEqual = require('deep-equal')
module.exports = Server
function Server (opts) {
this.mdns = multicastdns(opts)
this.mdns.setMaxListeners(0)
this.registry = {}
this.mdns.on('query', this._respondToQuery.bind(this))
}
Server.prototype.register = function (records) {
var self = this
if (Array.isArray(records)) records.forEach(register)
else register(records)
function register (record) {
var subRegistry = self.registry[record.type]
if (!subRegistry) subRegistry = self.registry[record.type] = []
else if (subRegistry.some(isDuplicateRecord(record))) return
subRegistry.push(record)
}
}
Server.prototype.unregister = function (records) {
var self = this
if (Array.isArray(records)) records.forEach(unregister)
else unregister(records)
function unregister (record) {
var type = record.type
if (!(type in self.registry)) return
self.registry[type] = self.registry[type].filter(function (r) {
return r.name !== record.name
})
}
}
Server.prototype._respondToQuery = function (query) {
var self = this
query.questions.forEach(function (question) {
var type = question.type
var name = question.name
// generate the answers section
var answers = type === 'ANY'
? flatten.depth(Object.keys(self.registry).map(self._recordsFor.bind(self, name)), 1)
: self._recordsFor(name, type)
if (answers.length === 0) return
// generate the additionals section
var additionals = []
if (type !== 'ANY') {
answers.forEach(function (answer) {
if (answer.type !== 'PTR') return
additionals = additionals
.concat(self._recordsFor(answer.data, 'SRV'))
.concat(self._recordsFor(answer.data, 'TXT'))
})
// to populate the A and AAAA records, we need to get a set of unique
// targets from the SRV record
additionals
.filter(function (record) {
return record.type === 'SRV'
})
.map(function (record) {
return record.data.target
})
.filter(unique())
.forEach(function (target) {
additionals = additionals
.concat(self._recordsFor(target, 'A'))
.concat(self._recordsFor(target, 'AAAA'))
})
}
self.mdns.respond({ answers: answers, additionals: additionals }, function (err) {
if (err) throw err // TODO: Handle this (if no callback is given, the error will be ignored)
})
})
}
Server.prototype._recordsFor = function (name, type) {
if (!(type in this.registry)) return []
return this.registry[type].filter(function (record) {
var _name = ~name.indexOf('.') ? record.name : record.name.split('.')[0]
return dnsEqual(_name, name)
})
}
function isDuplicateRecord (a) {
return function (b) {
return a.type === b.type &&
a.name === b.name &&
deepEqual(a.data, b.data)
}
}
function unique () {
var set = []
return function (obj) {
if (~set.indexOf(obj)) return false
set.push(obj)
return true
}
}