Uses the DNS protocol to resolve regular expression-based records (NAPTR records) for the hostname. The addresses argument passed to the callback function will contain an array of objects with the following properties:
flagsserviceregexpreplacementorderpreference
{
flags: 's',
service: 'SIP+D2U',
regexp: '',
replacement: '_sip._udp.example.com',
order: 30,
preference: 100
}