Develop Reference

How to keep track of sockets in nodejs?

I am trying to keep track of all tcp connections that are made in my server and store it in an array.
My problem begins when some connection is closed, in this situation I should delete it from my array but I can't do it. Can anyone help me? How do I delete a socket that is stored in my array?
var net = require("net");
function Server(port) {
var self = this;
this.conections = [];
this.server = net.createServer(function(socket) {
self.conections.push(socket); //storing the socket in the array
})
this.server.listen(port);
console.log("TCP Server created on port: "+ port);
}
module.exports = Server;

After thinking for a while I realized that I could give an ID to each socket, this way I can monitor each new connection in an array and delete it in case the connection is lost.
var net = require("net");
function Server(port) {
var self = this;
this.connections = [];
this.connectionsId = 0;
this.server = net.createServer(function(socket) {
socket.id = self.connectionsId++;
self.connections.push(socket); //storing the socket in the array
})
//Event that is always trigger when the connection is ended
socket.on('close', function() {
self.connections = self.connections.filter(function(conn) {
return conn.id !== socket.id;
});
});
this.server.listen(port);
console.log("TCP Server created on port: "+ port);
}
module.exports = Server;
Hope it helps somebody!

Cannot connect or emit to Amazon ECS Socket.io Server via Socket.io from a HTML file located in S3 bucket

I am having trouble connecting and emitting to an ECS Fargate Socket.io Server on AWS via Socket.io from a HTML file located in a S3 bucket in the same AWS region.
The ECS Fargate Server's code is as follows:
var app = require('express')();
var http = require('http').createServer(app);
var io = require('socket.io')(http);
var AWS = require ('aws-sdk');
io.on('connect', function (socket){
console.log('connection made');
socket.on('disconnect', function (socketds) {
console.log("***********************************************");
console.log("Disconnected");
});
socket.on('reconnect', function (socketds) {
console.log("***********************************************");
console.log("Reconnected");
});
socket.on('c_status', function () {
console.log("*********************************************");
console.log("cstatus");
});
socket.on('app_message', function (mdata) {
console.log("***********************************************");
console.log("App-message:",mdata);
socket.emit('command1',mdata);
});
});
http.listen(3000, function () {
console.log('listening on *:3000');
});
And the relevant code of the HTML file is as follows:
<script>
const serverLocation = "http://application-load-balancer-dns-link:3000";
const socket = io(serverLocation);
function sendmsg() {
var date = new Date();
date.setHours(date.getHours() + 4);
var datetm = date.toISOString().split('.')[0]+"Z";
var node_id = $('#innode').val();
var clid = "0";
var msg = $('#message').val();
if (node_id.length === 1) {
var unitcode = "0" + "0" + node_id;
}
else if (node_id.length === 2) {
var unitcode = "0" + node_id;
}
else {
var unitcode = node_id;
}
var mdata = datetm+unitcode+msg;
socket.emit('app_message',mdata);
}
</script>
I have been at it for 2 days now and have not been able to figure it out. It just doesn't connect.
Any help is greatly appreciated.
If you need more information, please let me know.

1) Try checking the inbound rules of the security group associated with that instance.
2) Outbound rules should also be configured as its bidirectional (By Default allows all)
3) If they are perfect. Check whether timeout occurs or any other exception.

io.sockets.in(room).emit() not working

For some reason when I want to emit to sockets in a given room I get nothing. It does work when I emit just to one specific socket, however. Here is my code:
//client side
var socket = io();
var room = "abc";
startButton.onclick = function(){
socket.emit('startGame',{room:room});
}
socket.on('startGameResponse', function(msg){
console.log(msg);
});
//server side
var serv = require('http').Server(app);
var io = require('socket.io')(serv,{});
io.sockets.on('connection', function(socket){
socket.on('startGame',function(data){
var room = data.room;
socket.join(room);
io.sockets.in(room).emit('startGameResponse','player joined');
}

Node JS and Socket IO

I'm trying to write an object with member functions for receiving and sending data to and from the client with Node JS and Socket IO. The problem is that every time I send data from the client, there is a new 'connection' event that fires. Is that how it works? I thought the connection event would only occur on a new connection. So with the code below, the log echoes 'New connection' with every reception from the client. It doesn't seem right.
io.sockets.on('connection', function (socket) {
console.log('New connection');
var localSocket = socket;
var newsock = new UserSocket(localSocket);
newsock.game = null;
newsock.host = null;
newsock.opponent = null;
newsock.room = "";
newsock.SendToHostSocket('Welcome to Baseball Strategy II');
arrSockets.push(socket);
});
function UserSocket(sock) {
var localSock = sock;
var o = this;
this.sock = localSock;
this.sock.on('clientData', function (data) {
console.log("user socket object");
console.log(o);
o.ParseClientData(data);
});
}
This is a simplified version of what I have for the client:
$(document).ready( function () {
var socket = io.connect('http://local.baseball.com:3333');
function SocketGameOut(outstring) {
socket.emit('clientData', outstring );
}
$("#hostGame").click( function () {
var gamenum = $('input[name=gameSelect]:checked', '#gameForm').val();
var aSendData = { command : "newgame" , senddata : { gameid : gamenum } };
var senddata = JSON.stringify(aSendData);
SocketGameOut(senddata);
});
});

Modify your code as below it worked for me.
//use once.('connection') instead of on.('connection')
io.sockets.once('connection', function (socket) {
console.log('New connection');
var localSocket = socket;
var newsock = new UserSocket(localSocket);
newsock.game = null;
newsock.host = null;
newsock.opponent = null;
newsock.room = "";
newsock.SendToHostSocket('Welcome to Baseball Strategy II');
arrSockets.push(socket);
});

Socket.io custom client ID

I'm making a chat app with socket.io, and I'd like to use my custom client id, instead of the default ones (8411473621394412707, 1120516437992682114). Is there any ways of sending the custom identifier when connecting or just using something to track a custom name for each ID? Thanks!

You can create an array on the server, and store custom objects on it. For example, you could store the id created by Socket.io and a custom ID sent by each client to the server:
var util = require("util"),
io = require('/socket.io').listen(8080),
fs = require('fs'),
os = require('os'),
url = require('url');
var clients =[];
io.sockets.on('connection', function (socket) {
socket.on('storeClientInfo', function (data) {
var clientInfo = new Object();
clientInfo.customId = data.customId;
clientInfo.clientId = socket.id;
clients.push(clientInfo);
});
socket.on('disconnect', function (data) {
for( var i=0, len=clients.length; i<len; ++i ){
var c = clients[i];
if(c.clientId == socket.id){
clients.splice(i,1);
break;
}
}
});
});
in this example, you need to call storeClientInfo from each client.
<script>
var socket = io.connect('http://localhost', {port: 8080});
socket.on('connect', function (data) {
socket.emit('storeClientInfo', { customId:"000CustomIdHere0000" });
});
</script>
Hope this helps.

To set custom socket id, generateId function must be overwritten. Both of eio and engine props of Socket.io server object can be used for to manage this operation.
A simple example:
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);
io.engine.generateId = function (req) {
// generate a new custom id here
return 1
}
io.on('connection', function (socket) {
console.log(socket.id); // writes 1 on the console
})
It seems to be it has been handled.
It must be in mind that socket id must be unpredictable and unique value with considering security and the app operations!
Extra: If socket.id is returned as undefined because of your intense processes on your generateId method, async/await combination can be used to overcome this issue on node.js version 7.6.0 and later. handshake method of node_modules/engine.io/lib/server.js file should be changed as following:
current:
// engine.io/lib/server.js
Server.prototype.generateId = function (req) {
return base64id.generateId();
};
Server.prototype.handshake = function (transportName, req) {
var id = this.generateId(req);
...
}
new:
// function assignment
io.engine.generateId = function (req) {
return new Promise(function (resolve, reject) {
let id;
// some intense id generation processes
// ...
resolve(id);
});
};
// engine.io/lib/server.js
Server.prototype.handshake = async function (transportName, req) {
var id = await this.generateId(req);
...
}
Note: At Engine.io v4.0, generateId method would accept a callback. So it would not needed to change handshake method. Only generateId method replacement is going to be enough. For instance:
io.engine.generateId = function (req, callback) {
// some intense id generation processes
// ...
callback(id);
};

In the newest socket.io (version 1.x) you can do something like this
socket = io.connect('http://localhost');
socket.on('connect', function() {
console.log(socket.io.engine.id); // old ID
socket.io.engine.id = 'new ID';
console.log(socket.io.engine.id); // new ID
});

I would use an object as a hash lookup - this will save you looping through an array
var clients = {};
clients[customId] = clientId;
var lookup = clients[customId];

Do not change the socket IDs to ones of your own choosing, it breaks the Socket.io room system entirely. It will fail silently and you'll have no clue why your clients aren't receiving the messages.

This will work with 2.2.0 and above version of Socket.IO
To set custom Socket Id, generateId function must be overwritten.
A simple example:
Server Side
var app = require('express')();
var http = require('http').Server(app);
var io = require('socket.io')(http);
io.use((socket, next) => {
io.engine.generateId = () => {
// USE ONE OF THESE
socket.handshake.query.CustomId; // this work for me
// return socket.handshake.query.CustomId;
}
next(null, true);
});
io.on('connection', function (socket) {
console.log(socket.id);
})
Clint Side
io.connect(URL, { query: "CustomId = CUSTOM ID IS HERE" })
NOTE: Keep in mind that socket id must be a unique value.

why not a simpler solution that does not need to maintain an array of connected clients and does not override internal socket id?
io.on("connection", (socket) => {
socket.on('storeClientInfo', (data) => {
console.log("connected custom id:", data.customId);
socket.customId = data.customId;
});
socket.on("disconnect", () => {
console.log("disconnected custom id:", socket.customId);
})
});
Client side
let customId = "your_custom_device_id";
socket.on("connect", () => {
socket.emit('storeClientInfo', { customId: customId });
});

or you can override the socket id, like this:
io.on('connection', function(socket){
socket.id = "YOUR_CUSTOM_ID";
});
you can see under the array:
io.sockets.sockets

Can store customId (example userId) in object format instead of for loop, this will improve performance during connection, disconnect and retrieving socketId for emitting
`
var userId_SocketId_KeyPair = {};
var socketId_UserId_KeyPair = {};
_io.on('connection', (socket) => {
console.log('Client connected');
//On socket disconnect
socket.on('disconnect', () => {
// Removing sockets
let socketId = socket.id;
let userId = socketId_UserId_KeyPair[socketId];
delete socketId_UserId_KeyPair[socketId];
if (userId != undefined) {
delete userId_SocketId_KeyPair[userId];
}
console.log("onDisconnect deleted socket with userId :" + "\nUserId,socketId :" + userId + "," + socketId);
});
//Store client info
socket.on('storeClientInfo', function (data) {
let jsonObject = JSON.parse(data);
let userId = jsonObject.userId;
let socketId = socket.id;
userId_SocketId_KeyPair[userId] = socketId;
socketId_UserId_KeyPair[socketId] = userId;
console.log("storeClientInfo called with :" + data + "\nUserId,socketId :" + userId + "," + socketId);
});
`

With this 2.2.0 version of Socket.IO, you can achieve this.
io.use((socket, next) => {
io.engine.generateId = () => socket.handshake.query.token;
next(null, true);
});

If you are trying to use a custom id to in order to communicate with a specific client then you can do this
io.on('connection', function(socket){
socket.id = "someId"
io.sockets.connected["someId"] = io.sockets.connected[socket.id];
// them emit to it by id like this
io.sockets.connected["someId"].emit("some message", "message content")
});