socket.io private message - node.js

Question

I've beeen scouring the Net with no luck. I'm trying to figure out how to send a private message from one user to another. There are lots of snippets, but I'm not sure about the client/server interaction. If I have the ID of the socket I want to send to, how do I send it to the server, and how do I ensure the server only sends the message to that one receiver socket?
Is there a tutorial or walkthrough that anyone knows of?

Answer 1

No tutorial needed. The Socket.IO FAQ is pretty straightforward on this one:
socket.emit('news', { hello: 'world' });
EDIT: Folks are linking to this question when asking about how to get that socket object later. There is no need to. When a new client connects, save a reference to that socket on whatever object you're keeping your user information on. My comment from below:
In the top of your script somewhere, setup an object to hold your users' information.
var connectedUsers = {};
In your .on('connection') function, add that socket to your new object. connectedUsers[USER_NAME_HERE] = socket; Then you can easily retrieve it later. connectedUsers[USER_NAME_HERE].emit('something', 'something');

Answer 2

Here's a code snippet that should help:
Client-side (sending message)
socket.emit("private", { msg: chatMsg.val(), to: selected.text() });
where to refers to the id to send a private message to and msg is the content.
Client-side (receiving message)
socket.on("private", function(data) {
chatLog.append('<li class="private"><em><strong>'+ data.from +' -> '+ data.to +'</strong>: '+ data.msg +'</em></li>');
});
where chatLog is a div displaying the chat messages.
Server-side
client.on("private", function(data) {
io.sockets.sockets[data.to].emit("private", { from: client.id, to: data.to, msg: data.msg });
client.emit("private", { from: client.id, to: data.to, msg: data.msg });
});

Answer 3

Although we have nice answers here. However, I couldn't grasp the whole client server unique user identification pretty fast, so I'm posting this simple steps in order to help whoever is struggling as i did.....
At the client side, Get the user's ID, in my case I'm getting the username...
Client side user registration
//Connect socket.io
var systemUrl = 'http://localhost:4000';
var socket = io.connect(systemUrl);
//Collect User identity from the client side
var username = prompt('Enter your Username');
socket.emit('register',username);
The Listen to register on the server side to register user's socket to connected socket
Serve side code User registration
/*Craete an empty object to collect connected users*/
var connectedUsers = {};
io.on('connection',function(socket){
/*Register connected user*/
socket.on('register',function(username){
socket.username = username;
connectedUsers[username] = socket;
});
});
Send Message from the client side
$(document).on('click','.username',function(){
var username = $(this).text(),
message = prompt("type your message");
socket.emit('private_chat',{
to : username,
message : message
});
});
Receive message on server and emit it to private user
/*Private chat*/
socket.on('private_chat',function(data){
const to = data.to,
message = data.message;
if(connectedUsers.hasOwnProperty(to)){
connectedUsers[to].emit('private_chat',{
//The sender's username
username : socket.username,
//Message sent to receiver
message : message
});
}
});
Receive message on client and display it
/*Received private messages*/
socket.on('private_chat',function(data){
var username = data.username;
var message = data.message;
alert(username+': '+message);
});
This is not the best, however you can start from here....

Answer 4

The easiest way I can think of is to have an hash of all the users on using their id or name as the key and have their socket as part of the value then when you want to send a message to just them you pull that socket and emit on it... something like this:
users[toUser].emit('msg',"Hello, "+toUser+"!");

Answer 5

if you have a web site that has register users with uid then you can create a room for each user and name the room by uid of the user.
first connect client to the server using :
var socket = io('server_url');
on the server side create an event for detecting client connection:
io.on('connection', function (socket) {}
then you can emit to client inside it using socket.emit(); and ask uid of current user.
on the client side create an event for this request and then send uid of the user to server.
now on server side join the connected socket to room using :
socket.join(uid);
console.log('user ' + socket.user + ' connected \n');
now you can send private message to a user using following line:
io.to(uid).emit();
if you use the code above, it doesn't matter how many tab user has already open from your web site . each tab will connect to the same room.

Answer 6

in socket.io 1.0 use
io.sockets.connected[<socketid>]
you can store just socket id. like so:
var users = {};
users[USER_NAME] = socket.id;
then:
io.sockets.connected[users[USER_NAME]]
.emit('private', {
msg:'private message for user with name '+ USER_NAME
});

Answer 7

You can create an unique room for messaging between USER_A and USER_B and both users must join to this room. You may use an UUID as a ROOM_ID (the 'socketId' in the following example).
io.on('connection', socket => {
socket.on('message', message => {
socket.to(message.socketId).emit('message', message);
});
socket.on('join', socketId => {
socket.join(socketId);
});
});
See Joining Rooms and Emit Cheatsheet

Answer 8

The way I got it to work is by introducing one more event "registered user". This basically triggers on the client side as soon as there is a registered user and then emits this even and passes "currentUser._id"
Client Side:
var socket = io();
<% if (currentUser) { %>
socket.emit('registered user', "<%= currentUser._id %>");
<% } %>
Server Side: Once the "registered user" even triggers, it joins the current user socket to the new room with the name which is that user id. So basically each registered user will be in a room which is his/her uid.
socket.on('registered user', function (uid) {
socket.join(uid)
});
Server Side: One there is a message sent, I pass the id of the user the message is sent to in the msg object and then emit to that specific room.
// Private chat
socket.on('chat message', function (msg) {
const uidTo = msg.uidTo
socket.in(uidTo).emit('chat message', msg )
}); `
});