使用mongoDB和socket.io处理Express中的POST

Question

我有一个非常奇怪的问题，我会尝试解释它： 我向服务器发送一个POST请求，然后将数据保存在数据库中，我将这些函数导出到一个单独的文件中。我怎样才能发出通过socket保存的内容，因为我的./database.js中不能要求（'socket.io'）？

这是一个片段：

var app = require('express')();
var database = require('./database');
var serv = require('http').createServer(app);
var socket = require('socket.io')(serv);
....

app.post('/test', function(req, res){
    database.save(model, req.body, res); //it saves the body to mongo and it works
    *edit//If I paste the code of database.save() here as is I can invoke emit
    //Here I want to emit the same data too
    //If I use the following I am receiving Error: Can't set headers after they are sent.
     socket.emit('value', JSON.stringify(req.body));
};