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

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.

SURE: Simply,

This is what you need :

io.to(socket.id).emit("event", data);

whenever a user joined to the server, socket details will be generated including ID. This is the ID really helps to send a message to particular people.

first we need to store all the socket.ids in array,

var people={};

people[name] =  socket.id;

here name is the receiver name. Example:

people["ccccc"]=2387423cjhgfwerwer23;

So, now we can get that socket.id with the receiver name whenever we are sending message:

for this we need to know the receivername. You need to emit receiver name to the server.

final thing is:

 socket.on('chat message', function(data){
io.to(people[data.receiver]).emit('chat message', data.msg);
});

Hope this works well for you.

Good Luck!!

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.