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

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);
};