Send update notification to particular users using socket.io - node.js

Question

Following is the code on front end, where storeSelUserId contains user_id to send the message-
FYI - Node Version 1.1.0
// Socket Notification
var socket = io('http://localhost:6868');
socket.on('connection', function (data) {
socket.emit('send notification', { sent_to: storeSelUserId });
});
Following is the server code in routes file -
var clients = {};
io.on('connection', function (socket) {
socket.emit('connection', "Connection Created.");
socket.on('send notification', function (sent_to) {
console.log(sent_to);
});
});
In console sent_to is showing the array of user_id.
Now being a starter in socket.io I stuck with the solution that how do I send the message to these particular userids.
I search and found that I need to push each user with its sockets so I reformed it to -
var users = [];
io.on('connection', function (socket) {
users.push({socket_id: socket.id});
socket.emit('connection', "Connection Created.");
socket.on('send notification', function (sent_to) {
console.log(sent_to);
});
});
But I am in dilemma that else do I need to do to store which user_id refers to which socket_id and then update the div of users with that particular ids?
EDIT -
Add Controller - (Front End)
Front end Interface where memo is created and send to particular users
var socket = io('http://localhost:6868');
socket.on('connection', function (data) {
socket.emit('send memo notification', {creator_id: creator_id, sent_to: [Array of user_ids to whom memo to send]});
});
Dashboard controller - (Front End)
Front end Interface where notification count to show "notificationCount"
if (SessionService.currentUser._id) {
var socket = io('http://localhost:6868');
socket.on('connection', function (data) {
socket.emit('get notifications', {user_id: SessionService.currentUser._id});
});
socket.on('notification data', function(data){
console.log("-- Not Data Test -");
$scope.notificationCount = data.length;
});
}
Code at server end -
io.on('connection', function (socket) {
socket.emit('connection', "Connection Created.");
socket.on('send memo notification', function(data) {
notifications.createNotification(data);
});
socket.on('get notifications', function(data){
notifications.getNotifications(data, function(response){
socket.emit('notification data', response.data);
});
});
});
Backend controller code -
exports.getNotifications = function(data, callback) {
var userId = data.user_id;
Notification.find({receiver_id: userId}, function(err, response){
if (err)
callback({"message": "error", "data": err, "status_code": "500"});
else
callback({"message": "success", "data": response, "status_code": "200"});
});
};
exports.createNotification = function(data) {
var notificationData = data;
var x = 0;
for(var i=0; i< notificationData.length; i++) {
// Code
Notification(notificationData[i]).save(function(err,response){
if (err)
return false;
});
if (x === notificationData.length - 1) {
return true;
}
x++;
}
};

Answer 1

If you want to use your own user ids then there is no way around mapping the socket id to the user id. I assume a client knows its user id from somewhere, so it could send its user id to the server after connection.
Client
socket.on('connection', function (data) {
socket.emit('setUserId', myUserId);
});
The server saves the socket for each user id.
socket.on('setUserId', function (userId) {
users[userId]=socket;
});
If you have such a mapping in the server you can send a message just to this client using the user id.
socket.on('send notification', function (userId) {
users[userId].emit('notification', "important notification message");
});
Edit: Saving the corresponding socket directly is even better.

Answer 2

According to what i understand, you need private notification send to only some users. For that, save your users name to whom you want to send and their corresponding socket in different hashes.
username [socket.name] = username to be added;
usersocket [ socket.name ] =socket;
Then to emit the messages to that user only, use
usersocket[ socket.name ].emit('event for send message', ' what you want to send ');