Socket.io is closed before the connection is established - node.js

Question

I use in my app mongoose.js and socket.io. I try to emit an event in a mongoose callback. But my client (angular) does not seem to receive anything. Besides, it is continuously disconnected every time an event is emitted server side, in the callback and with 'user' data.
To be precise, my User model is wrapped in the following manner :
const mongoose = require('mongoose')
class DBReader {
constructor(name, schema) {
this.Model = require(`./models/${name}`)
}
find(params, callback) {
this.Model.find(params, callback)
}
findOne(params, callback) {
this.Model.findOne(params, callback)
}
findById(id, callback) {
this.Model.findById(id, callback)
}
}
module.exports = DBReader
And I instantiate my user like this :
const User = new DBReader('user')
The following code works, that is to say my client is not disconnected and receives the two events (It works because I don't emit 'user' data in the callback)...
function socket(httpServer) {
const io = require('socket.io')(httpServer)
io.on('connection', socket => {
console.log('User connected')
socket.emit('hello', 'Hello World !')
User.findOne({}, (err, user) => {
console.log(err)
console.log(user) // Displays the requested user
})
socket.emit('hello', 'Wooorld !')
socket.on('disconnect', () => {
console.log('User disconnected')
})
})
}
This code works too (because I don't emit 'user' data).
function socket(httpServer) {
const io = socketio(httpServer)
io.on('connection', socket => {
console.log('User connected')
socket.emit('hello', 'Hello World !')
User.findOne({}, (err, user) => {
console.log(err)
console.log(user)
socket.emit('hello', 'hellooo !')
})
socket.emit('hello', 'Wooorld !')
socket.on('disconnect', () => {
console.log('User disconnected')
})
})
}
But this code does not work (event emitted in the callback with 'user' data)...
function socket(httpServer) {
const io = socketio(httpServer)
io.on('connection', socket => {
console.log('User connected')
socket.emit('hello', 'Hello World !')
User.findOne({}, (err, user) => {
console.log(err)
console.log(user)
socket.emit('hello', user)
})
socket.emit('hello', 'Wooorld !')
socket.on('disconnect', () => {
console.log('User disconnected')
})
})
}
Do you have any explanation ? Do you need further information ?

Answer 1

I found the answer -_- !
Actually, it turned out I could not send accents (é, è, à...). And that is because my client side socket.io package was older than the server side one (1.7.? against 2.0.3).
I hope this answer will at least help the next person trying to emit an object with accents...

Answer 2

you can only emit something that can be stringified via JSON.stringify ( -> no circular references). As you are trying to send down the whole mongooseDocument, that will fail.
Either you can do a mongooseModel.find({...}).lean().exec(function callback(err, user){...}) which will return you a plain javascript object instead of the mongooseDocument (which can be serialized) or you can use the mongoose.toJSON method to convert it yourself.
regarding the problems of socket.io/angular, I can't help as you provided not enough code