How to send a message to a particular client with socket.io

Question

I'm starting with socket.io + node.js, I know how to send a message locally and to broadcast socket.broadcast.emit() function:- all the connected clients receive the same message.

Now, I would like to know how to send a private message to a particular client, I mean one socket for a private chat between 2 person (Client-To-Client stream). Thanks.

Answer 1

You can use socket.io rooms. From the client side emit an event ("join" in this case, can be anything) with any unique identifier (email, id).

Client Side:

var socket = io.connect('http://localhost'); socket.emit('join', {email: [email protected]}); 

Now, from the server side use that information to create an unique room for that user

Server Side:

var io = require('socket.io').listen(80);  io.sockets.on('connection', function (socket) {   socket.on('join', function (data) {     socket.join(data.email); // We are using room of socket io   }); }); 

So, now every user has joined a room named after user's email. So if you want to send a specific user a message you just have to

Server Side:

io.sockets.in('[email protected]').emit('new_msg', {msg: 'hello'}); 

The last thing left to do on the client side is listen to the "new_msg" event.

Client Side:

socket.on("new_msg", function(data) {     alert(data.msg); } 

I hope you get the idea.

Answer 2

When a user connects, it should send a message to the server with a username which has to be unique, like an email.

A pair of username and socket should be stored in an object like this:

var users = {     '[email protected]': [socket object],     '[email protected]': [socket object],     '[email protected]': [socket object] } 

On the client, emit an object to the server with the following data:

{     to:[the other receiver's username as a string],     from:[the person who sent the message as string],     message:[the message to be sent as string] } 

On the server, listen for messages. When a message is received, emit the data to the receiver.

users[data.to].emit('receivedMessage', data) 

On the client, listen for emits from the server called 'receivedMessage', and by reading the data you can handle who it came from and the message that was sent.