NodeJS concurrent web server

I'm creating NodeJS App which calls 5 external Web service APIs.
then results are processed and output is generated on nodeJS/express web server.

it can not handle 200 concurrent users. it does serve output but after 30 seconds.
ETIMEDOUT and ESOCKETIMEDOUT errors are generated in web service calls.

i have set sysctl.conf to maximum and http.globalAgent.maxSockets=Infinity;utilizing all cores
but still its not working.

Same server running PHP can serve 1000 concurrent connections.
Simple Webserver can't serve 200 concurrent connections.

var http = require('http');
http.globalAgent.maxSockets=Infinity;

http.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/plain'});
res.end('Hello World\n');
}).listen(1337);
console.log('Server running at http://127.0.0.1:1337/');