Socket.io custom client ID

Question

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

Answer 1

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);
    });
`

Answer 2

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")
});

Answer 3

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 });
});

Answer 4

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);
};

Answer 5

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
});

Answer 6

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.