用http模块访问后端失败，求解原因

这是用来访问的代码：

var http = require('http');
var req = http.request({
    method: 'POST',
    port: 3000,
    headers: {
         'Content-Type': 'application/json'
    }
},function(res){
    console.log(res);
});

req.write('{"foo":"');
var n=300000;

while (n--){
    req.write('foo,');
}

req.end('bar"}');
console.log("over");

下面是后端代码：

var connect = require('connect');
var bodyParser =require("body-parser");
var app = connect();

app.use(function(res,req,next){
    console.log("start");
    next();
});
app.use(bodyParser());
app.use(function(req,res){
    console.log(req.body.foo);
    res.end("ok\n");
}).listen(3000);

都运行后，结果什么事情都没发生