Getting client hostname in Node.js

You can use the 'dns' module to do a reverse dns lookup:

require('dns').reverse('12.12.12.12', function(err, domains) {
    if(err) {
        console.log(err.toString());
        return;
    }
    console.log(domains);
});

See: http://nodejs.org/docs/v0.3.1/api/all.html#dns.reverse

I think this might help you. That's not exactly the client hostname but the ip address.

function getClientAddress(req) {
  return req.headers['x-forwarded-for'] || req.connection.remoteAddress;
}

I think the only way you can do it is like this:

<form method="post" action="/gethostname">
    <label for="hostname">What is your hostname?</label>
    <input type="text" name="hostname" id="hostname">
</form>

But I would suggest you don't really need it, it's not like you can do anything useful with the information. If you just want a string to identify with the user's machine then you can make something up.

If what you're really after is the FQDN then I would suggest it's still not really that useful to you, but for that you need Reverse DNS lookup. If you're on a VPS or similar you can probably configure your box to do this for you, but note that it'll likely take a few seconds so it's not a good idea to do it as part of a response. Also note, you'll not be getting the user's machine's FQDN in most cases but that of their router.