Connection socket.io incremented after stopping the server - node.js

Question

I have a problem with socket.io from nodeJs.
I am trying to create a connection from a client to a server. Once the client is connected, the server sends a message to the client (ack).
Until then, everything works fine but when I disconnect the server and restart it, it sends me the message twice to the client.
If I repeat the manipulation a third time, three messages will appear.
I have captured the problem:
client.js
var socket = require('socket.io-client')('http://localhost:8050', {
'forceNew':true
});
socket.on('connect', onConnect);
function onConnect(){
console.log('connect ' + socket.id);
socket.emit('sendConnect','First connect');
socket.on("ack", function(data) {
console.log("ack reçu");
});
socket.on('disconnect', function(reason) {
console.log(reason);
});
}
server.js
var io = require("socket.io");
var sockets = io.listen(8050);
sockets.on('connection', function (socket) {
socket.on('sendConnect', function (data) {
console.log("message :" + data);
socket.emit('ack');
socket.on('disconnect', function() {
console.log('Got disconnect!');
});
});
});
I looked if this bug was already arriving without finding an answer.
I must surely be doing something wrong!
Thank you in advance for your help.

Answer 1

Your onConnect function adds new event listeners each time the socket connects. Move the event subscriptions out of onConnect like this:
var socket = require('socket.io-client')('http://localhost:8050', {
forceNew: true
});
socket.on('connect', onConnect);
socket.on('ack', function(data) {
console.log('ack reçu');
});
socket.on('disconnect', function(reason) {
console.log(reason);
});
function onConnect() {
console.log('connect ' + socket.id);
socket.emit('sendConnect', 'First connect');
}