DNS query in Java

Question

I am messing around with DNS services in Java. I am specifically trying to look up all google.com addresses and display them in an array, similar to running a lookup using nslookup:

nslookup -q=TXT _netblocks.google.com 8.8.8.8

I am using InetAddress for this but I keep on getting exceptions. Since the exceptions refer to an 'Unknown Host', I don't think InetAddress can read TXT records (if I use google.com it works, but that doesn't show the full IP range).

Below is my code:

InetAddress dnsresult[] = InetAddress.getAllByName("_netblocks.google.com");

for (int i=0; i<dnsresult.length; i++)
    System.out.println(dnsresult[i]);

I would appreciate it if someone could point me in the right direction.

Regeneration

This problem may not be Java related only since my ping also can't resolve _netblocks.google.com. – Termite

Thanks Zhedar, I know that :) I added that to illustrate what I am trying to do. If I use 'google.com' as my argument, it does pop out an IP. But that is the A record. I need to grab the TXT record. – Regeneration

Answer 1

You cannot lookup TXT or other DNS records InetAddress class. InetAddress.getAllByName() looks up for A, or AAAA records only.

Check DNS Java for your needs.

Misfeasance

Answer 2

Here is an example that does what you are trying to do:

Attribute attr = new InitialDirContext().getAttributes("dns:_netblocks.google.com", new String[] {"TXT"}).get("TXT");
System.out.println("attr.get() = " + attr.get());
System.out.println("attr.getAll() = " + Collections.list(attr.getAll()));

If you want to use a custom dns server use "dns://1.1/_netblocks.google.com" instead.

Vulpine

Answer 3

InetAddress doesn't do this, but you can accomplish DNS TXT record lookups in Java via the JNDI DNS provider.

Bisson

Answer 4

I ended up using Google's "JSON API for DNS over HTTPS (DoH)"

https://developers.google.com/speed/public-dns/docs/doh/json

Cambria