nodejs longpoll socket hang up error

Question

i have a small app (in Node.JS) that connects a bunch of longpolling connections to a server via https.request

 var data = "{'foo':'bar'}";  
 var options = {
        'host'               : '127.0.0.1',
        'port'               : '443',
        'path'               : '/push',
        'method'             : 'POST',
        'rejectUnauthorized' : false,
        'agent'              : false,
        'headers'            : {
            'Content-Type': 'application/json',
            'Content-Length': data.length
        }
    };
       var request = require('https').request(options, function(responseStream){

            responseStream.setEncoding('utf8');

            var responseData = "";
            responseStream.on('data', function (chunk) {
                responseData += chunk;
            });

            responseStream.on('end', function() {

                // trigger callback on master
                process.send({
                    "type"     : Constants.PROCESSORS.MESSAGE.REPLY,
                    "data"     : responseData
                });

            });

        });

        request.write(data);
        request.end();

the request inits, receives a socket, and after around ~20 seconds i receive a socket hang up error. it never reaches the 'connected' state ('connect' event not thrown).

error callstack:

"Error: socket hang up
at createHangUpError (_http_client.js:192:15)
at TLSSocket.socketOnEnd (_http_client.js:270:23)
at emitNone (events.js:70:20)
at TLSSocket.emit (events.js:147:7)
at _stream_readable.js:891:16
at process._tickCallback (node.js:337:11)"

EDIT: i forgot to mention that the remote server is a balancer that uses HAProxy, but i managed to reproduce this with a simple server (no balancer, just node.js web server)