multiple http connections to test NAT

Question

I'am in a project where i need to establish the most possible http connections and keep them open for nat port testing, using node.js but I'm not sure how I could do it, till now i got this:

var http = require('http');
var http_options = {
    hostname: '193.136.212.161',
    port: 80,
    path: '/',
    method: 'GET',
    agent: false,
    headers: {
       'Connection':'keep-alive'
    }
};

var req = http.request(http_options)
  .on("socket", function (socket) {
      console.log('got connected!');
   });
req.end();

unfortunely it closes the connection not keeping it alive, if i could have some tips to advance would be great.