dns.lookup(hostname[, options], callback)
Resolves a hostname (e.g. 'nodejs.org') into the first found A (IPv4) or AAAA (IPv6) record. options can be an object or integer. If options is not provided, then IPv4 and IPv6 addresses are both valid. If options is an integer, then it must be 4 or 6.
Alternatively, options can be an object containing these properties:
family {Number} - The record family. If present, must be the integer 4 or 6. If not provided, both IP v4 and v6 addresses are accept