how to get socket.id of a connection on client side?

Question

Im using the following code in index.js

io.on('connection', function(socket){ console.log('a user connected'); console.log(socket.id); }); 

the above code lets me print the socket.id in console.

But when i try to print the socket.id on client side using the following code

<script> var socket = io(); var id = socket.io.engine.id; document.write(id); </script> 

it gives 'null' as output in the browser.

Answer 1

You should wait for the event connect before accessing the id field:

With this parameter, you will access the sessionID

socket.id 

Edit with:

Client-side:

var socketConnection = io.connect(); socketConnection.on('connect', function() {   const sessionID = socketConnection.socket.sessionid; //   ... }); 

Server-side:

io.sockets.on('connect', function(socket) {   const sessionID = socket.id;   ... }); 

Answer 2

For Socket 2.0.4 users

Client Side

 let socket = io.connect('http://localhost:<portNumber>');   console.log(socket.id); // undefined  socket.on('connect', () => {     console.log(socket.id); // an alphanumeric id...  }); 

Server Side

 const io = require('socket.io')().listen(portNumber);  io.on('connection', function(socket){     console.log(socket.id); // same respective alphanumeric id...  }