Send Notification properly using Socket.io Redis server - angularjs

Question

OBJECTIVE: When post is added to perticular channel send notification to all connected subscribed users for that channel.
Relational Database tables over view: Post, Channels, Users, Channels_Users
Post: id, title, content, channel_id(Indicate post is related to what channel)
Channels: id, name (List of Channels)
Users: id, username (User Table)
Channels_Users: id, channel_id, user_id (This table indicate which channels user is subscribed to.)
Goal: When post is created, send notification to perticular user group.
I have tried serveral ways and it is working as aspected. But I am looking for the correct way of doing this.
Server Side: socket.js
Naming conventions:
Channel name:
channel-1, channel-2, channel-3, ....
Namespace name('namespace-'+[channelName]) :
namespace-channel-1, namespace-channel-2, ...
var app = require('express')();
var request = require('request');
var http = require('http').Server(app);
var io = require('socket.io').listen(http);
var Redis = require('ioredis');
var redis = new Redis(####, 'localhost');
// Get all channels from Database and loop through it
// subscribe to redis channel
// initialize namespace inorder to send message to it
for(var i=1; i=<50; i++) {
redis.subscribe('channel-'+i);
io.of('/namespace-channel-'+i).on('connection', function(socket){
console.log('user connected');
});
}
// We have been subscribed to redis channel so
// this block will hear if there is any new message from redis server
redis.on('message', function(channel, message) {
message = JSON.parse(message);
// send message to specific namespace, with event = newPost
io.of('/namespace-'+channel).emit('newPost', message.data);
});
//Listen
http.listen(3000, function(){
console.log('Listening on Port 3000');
});
Client side: Angularjs Socket factory code: (Mentioning main socket code)
// userChannels: user subscribed channels array
// Loop through all channel and hear for new Post and
// display notification if there is newPost event
userChannels.forEach(function (c) {
let socket = {};
console.info('Attempting to connect to namespace'+c);
socket = io.connect(SOCKET_URL + ':3000/namespace-'+c, {query: "Authorization=token"});
socket.on('connect',function(){
if(socket.connected){
console.info("namespace-" + c + " Connected!");
// On New post event for this name space
socket.on('newPost', function(data) {
/* DISPLAY DESKTOP NOTIFICATION */
});
}
});
});
Publish data to Redis server, at the time of new post created
$data = [
'event' => 'newPost',
'data' => [
'title' => $postTitle,
'content' => $postContent
]
];
$redisChannel = "channel-" . $channelId; // As per our naming conventions
Redis::publish($redisChannel, json_encode($data));
The user is getting notification correctly for the channels they have been subscribed.
Problem 1: I am not sure this is the best solution to implement this notification thing.
Problem 2: When a user opens the same application in more than one browser tabs, it gets the notification for all of them. It should send only one notification. This is something related to user management at server side on redis end. I am not sure about this part too.
I really appreciate your suggestion/help on this. Thank you in advance.