var packet = require('dns-packet')
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var dgram = require('dgram')
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var thunky = require('thunky')
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var events = require('events')
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var os = require('os')
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var noop = function () {}
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module.exports = function (opts) {
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if (!opts) opts = {}
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var that = new events.EventEmitter()
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var port = typeof opts.port === 'number' ? opts.port : 5353
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var type = opts.type || 'udp4'
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var ip = opts.ip || opts.host || (type === 'udp4' ? '224.0.0.251' : null)
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var me = {address: ip, port: port}
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var memberships = {}
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var destroyed = false
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var interval = null
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if (type === 'udp6' && (!ip || !opts.interface)) {
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throw new Error('For IPv6 multicast you must specify `ip` and `interface`')
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}
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var socket = opts.socket || dgram.createSocket({
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type: type,
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reuseAddr: opts.reuseAddr !== false,
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toString: function () {
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return type
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}
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})
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socket.on('error', function (err) {
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if (err.code === 'EACCES' || err.code === 'EADDRINUSE') that.emit('error', err)
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else that.emit('warning', err)
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})
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socket.on('message', function (message, rinfo) {
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try {
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message = packet.decode(message)
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} catch (err) {
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that.emit('warning', err)
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return
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}
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that.emit('packet', message, rinfo)
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if (message.type === 'query') that.emit('query', message, rinfo)
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if (message.type === 'response') that.emit('response', message, rinfo)
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})
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socket.on('listening', function () {
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if (!port) port = me.port = socket.address().port
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if (opts.multicast !== false) {
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that.update()
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interval = setInterval(that.update, 5000)
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socket.setMulticastTTL(opts.ttl || 255)
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socket.setMulticastLoopback(opts.loopback !== false)
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}
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})
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var bind = thunky(function (cb) {
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if (!port) return cb(null)
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socket.once('error', cb)
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socket.bind(port, opts.interface, function () {
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socket.removeListener('error', cb)
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cb(null)
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})
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})
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bind(function (err) {
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if (err) return that.emit('error', err)
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that.emit('ready')
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})
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that.send = function (value, rinfo, cb) {
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if (typeof rinfo === 'function') return that.send(value, null, rinfo)
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if (!cb) cb = noop
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if (!rinfo) rinfo = me
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bind(onbind)
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function onbind (err) {
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if (destroyed) return cb()
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if (err) return cb(err)
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var message = packet.encode(value)
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socket.send(message, 0, message.length, rinfo.port, rinfo.address || rinfo.host, cb)
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}
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}
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that.response =
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that.respond = function (res, rinfo, cb) {
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if (Array.isArray(res)) res = {answers: res}
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res.type = 'response'
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res.flags = (res.flags || 0) | packet.AUTHORITATIVE_ANSWER
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that.send(res, rinfo, cb)
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}
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that.query = function (q, type, rinfo, cb) {
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if (typeof type === 'function') return that.query(q, null, null, type)
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if (typeof type === 'object' && type && type.port) return that.query(q, null, type, rinfo)
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if (typeof rinfo === 'function') return that.query(q, type, null, rinfo)
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if (!cb) cb = noop
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if (typeof q === 'string') q = [{name: q, type: type || 'ANY'}]
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if (Array.isArray(q)) q = {type: 'query', questions: q}
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q.type = 'query'
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that.send(q, rinfo, cb)
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}
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that.destroy = function (cb) {
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if (!cb) cb = noop
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if (destroyed) return process.nextTick(cb)
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destroyed = true
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clearInterval(interval)
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socket.once('close', cb)
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socket.close()
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}
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that.update = function () {
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var ifaces = opts.interface ? [].concat(opts.interface) : allInterfaces()
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var updated = false
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for (var i = 0; i < ifaces.length; i++) {
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var addr = ifaces[i]
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if (memberships[addr]) continue
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memberships[addr] = true
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updated = true
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try {
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socket.addMembership(ip, addr)
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} catch (err) {
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that.emit('warning', err)
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}
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}
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if (!updated || !socket.setMulticastInterface) return
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socket.setMulticastInterface(opts.interface || defaultInterface())
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}
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return that
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}
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function defaultInterface () {
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var networks = os.networkInterfaces()
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var names = Object.keys(networks)
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for (var i = 0; i < names.length; i++) {
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var net = networks[names[i]]
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for (var j = 0; j < net.length; j++) {
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var iface = net[j]
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if (iface.family === 'IPv4' && !iface.internal) return iface.address
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}
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}
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return '127.0.0.1'
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}
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function allInterfaces () {
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var networks = os.networkInterfaces()
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var names = Object.keys(networks)
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var res = []
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for (var i = 0; i < names.length; i++) {
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var net = networks[names[i]]
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for (var j = 0; j < net.length; j++) {
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var iface = net[j]
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if (iface.family === 'IPv4') {
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res.push(iface.address)
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// could only addMembership once per interface (https://nodejs.org/api/dgram.html#dgram_socket_addmembership_multicastaddress_multicastinterface)
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break
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}
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}
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}
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return res
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}
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