Using socket io to get data realtime not working - node.js

Question

I'm new to mean-stack and I followed some instruction on how to get real-time data. I tried every single steps but none of it is working, how can I use socket.io correctly? I provided my code here for getting users from mongodb, please do correct my code
server.js
var express = require ('express');
var app = express();
var server = require('http').Server(app);
var http = require('http').Server(app);
var io = require('socket.io')(http);
var morgan = require ('morgan');
var mongoose = require('mongoose');
var appRoutes = require('./app/routes/api');
app.use(morgan('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(express.static(__dirname + '/public'));
app.use('/api',appRoutes);
mongoose.connect('mongodb://localhost:27017/testing', function(err){
if(err){
console.log('Not connected' + err);
} else
{
console.log('Connected');
}
});
Then here is the part where I get the users from the table, I don't know how to get the the data real-time:
api.js
var User = require('../models/user');
const router = express.Router();
router.get('/management', function(req, res) {
User.find({}, function(err, users) {
if (!users) {
res.json({ success: false, message: 'Users not found' });
} else {
res.json({ success: true, users: users,});
}
});
});
userCtrl.js
.controller('managementCtrl', function(User, $scope) {
function getUsers() {
User.getUsers().then(function(data) {
if (data.data.success) {
app.users = data.data.users;
} else {
app.errorMsg = data.data.message;
}
});
}
});
users.html
<tbody>
<tr ng-repeat="person in management.users">
<td align="center">{{ person.name }}</td>
<td align="center">{{ person.email }}</td>
</tr>
</tbody>

Answer 1

First of all you need to get a socket with connection event:
io.on('connect', function(socket){
than you need to set a "listener" on specific event you want to reply with data
Together it will be:
io.on('connect', function(socket){
socket.on('eventYouGet', function(eventData) {
User.find({}, function(err, users) {
if (!users) {
socket.emit('eventAnswer', {success: false, message: 'Users not found'});
} else {
socket.emit('eventAnswer', {success: true, users: users)};
}
});
});
});
Where eventYouGet is event which you (from server perspective) are waiting for (kind of like request in REST); eventAnswer is event you send as answer (to the client).
Note:
socket.emit sends an event to sender and no one else (one socket)

Answer 2

On the server -
I generally check for connections:
io.on('connection', function(socket){
console.log('a user connected');
});
You'll need for the client and the server to agree on some sort of token to listen to for socket. In this case, I am hardcoding in '123123123'
var User = require('../models/user');
const router = express.Router();
router.get('/management', function(req, res) {
User.find({}, function(err, users) {
if (!users) {
io.emit("123123123", { success: false, message: 'Users not found' });
} else {
io.emit("123123123", { success: true, users: users,});
}
});
});
In angular -
var socket = io.connect(<url>); //url from server
socket.on('123123123', function (user) {
let user = json.parse(user)
});