我正在尝试使用mdns节点模块实现zeroconf protocole，但是当我使用它时，我有这个错误（在raspberry pi 2上）：
error: Error: dns service error: unknown
at Error (native)
at new Advertisement (/var/www/lisa/node_modules/mdns/lib/advertisement.js:56:10)
at Object.create [as createAdvertisement] (/var/www/lisa/node_modules/mdns/lib/advertisement.js:64:10)
at Object.module.exports.bootstrap (/var/www/lisa/config/bootstrap.js:22:17)
at Sails.runBootstrap (/var/www/lisa/node_modules/sails/lib/app/private/bootstrap.js:44:25)
at Sails.bound [as runBootstrap] (/var/www/lisa/node_modules/sails/node_modules/lodash/dist/lodash.js:729:21)
at Sails.initialize (/var/www/lisa/node_modules/sails/lib/app/private/initialize.js:48:9)
at bound (/var/www/lisa/node_modules/sails/node_modules/lodash/dist/lodash.js:729:21)
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:607:21
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:246:17
at iterate (/var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:146:13)
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:157:25
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:248:21
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:612:34
at /var/www/lisa/node_modules/sails/lib/app/load.js:201:13
at /var/www/lisa/node_modules/sails/node_modules/async/lib/async.js:451:17
这是我的代码：
var mdns = require('mdns');
var txt_record = {
name : 'Test module'
};
var ad = mdns.createAdvertisement(mdns.tcp('http'), 4321, txt_record);
ad.start();