resolver.js

const dns = require('dns');

console.log(dns.getServers());


function getAddress(uri) {
    return new Promise(function(res, rej) {
        dns.resolve4(uri, function(err, address) {
            if (err) {
                rej(err);
            }
            res(address);
        });
    });
}


function makeResolver(uri) {
    let timeout;
    let lastResolvedAddress;

    function pingAndQueue () {
        getAddress(uri).then(function(addresses) {
            const addr = addresses.pop(); // multiple addresses?
            if (lastResolvedAddress !== addr) {
                console.log('ip changed:', addr);
                lastResolvedAddress = addr;
            } else {
                console.log('-');
            }

            timeout = setTimeout(pingAndQueue, 9000);
        }).catch(function(err) {
            clearTimeout(timeout);
            console.log('errr', err);
        });
    }
    pingAndQueue();
}

makeResolver('bip.local');