Update
The accepted answer was good for last year but today I would use the package everyone else uses: https://github.com/mikeal/request
This thread is old but I wanted to do same things with the https://github.com/mikeal/request package.
Here a working example
var fs = require('fs');
var request = require('request');
// Or with cookies
// var request = require('request').defaults({jar: true});
request.get({url: 'https://someurl/somefile.torrent', encoding: 'binary'}, function (err, response, body) {
fs.writeFile("/tmp/test.torrent", body, 'binary', function(err) {
if(err)
console.log(err);
else
console.log("The file was saved!");
});
});