Develop Reference

JS: Node.js and Socket.io - globals and architecture

Dear all,
Im working with JS for some weeks and now I need a bit of clarification. I have read a lot of sources and a lot of Q&A also in here and this is what I learned so far.
Everything below is in connection with Node.js and Socket.io
Use of globals in Node.js "can" be done, but is not best practice, terms: DONT DO IT!
With Sockets, everything is treated per socket call, meaning there is hardly a memory of previous call. Call gets in, and gets served, so no "kept" variables.
Ok I build up some chat example, multiple users - all get served with broadcast but no private messages for example.
Fairly simple and fairly ok. But now I am stuck in my mind and cant wrap my head around.
Lets say:
I need to act on the request
Like a request: "To all users whose name is BRIAN"
In my head I imagined:
1.
Custom object USER - defined globally on Node.js
function User(socket) {
this.Name;
this.socket = socket; }
2.
Than hold an ARRAY of these globally
users = [];
and on newConnection, create a new User, pass on its socket and store in the array for further action with
users.push(new User(socket));
3.
And on a Socket.io request that wants to contact all BRIANs do something like
for (var i = 0; i < users.length; i++) {
if(user[i].Name == "BRIAN") {
// Emit to user[i].socket
}}
But after trying and erroring, debugging, googling and reading apparently this is NOT how something like this should be done and somehow I cant find the right way to do it, or at least see / understand it. can you please help me, point me into a good direction or propose a best practice here? That would be awesome :-)
Note:
I dont want to store the data in a DB (that is next step) I want to work on the fly.
Thank you very much for your inputs
Oliver

first of all, please don't put users in a global variable, better put it in a module and require it elsewhere whenever needed. you can do it like this:
users.js
var users = {
_list : {}
};
users.create = function(data){
this._list[data.id] = data;
}
users.get = function(user_id){
return this._list[user_id];
};
users.getAll = function(){
return this._list;
};
module.exports = users;
and somewhere where in your implementation
var users = require('users');
For your problem where you want to send to all users with name "BRIAN",
i can see that you can do this good in 2 ways.
First.
When user is connected to socketio server, let the user join a socketio room using his/her name.
so it will look like this:
var custom_namespace = io.of('/custom_namespace');
custom_namespace.on('connection', function(client_socket){
//assuming here is where you send data from frontend to server
client_socket.on('user_data', function(data){
//assuming you have sent a valid object with a parameter "name", let the client socket join the room
if(data != undefined){
client_socket.join(data.name); //here is the trick
}
});
});
now, if you want to send to all people with name "BRIAN", you can achieve it by doing this
io.of('/custom_namespace').broadcast.to('BRIAN').emit('some_event',some_data);
Second.
By saving the data on the module users and filter it using lodash library
sample code
var _lodash = require('lodash');
var Users = require('users');
var all_users = Users.getAll();
var socket_ids = [];
var users_with_name_brian = _lodash.filter(all_users, { name : "BRIAN" });
users_with_name_brian.forEach(function(user){
socket_ids.push(user.name);
});
now instead of emitting it one by one per iteration, you can do it like this in socketio
io.of('/custom_namespace').broadcast.to(socket_ids).emit('some_event',some_data);
Here is the link for lodash documentation
I hope this helps.

Implement Server Side Events with Grails

I want to implement Server side events with grails. What i want is that only when there is a change in the DataBase my DataTable should refresh. I want to user HTML5 Server Side events for this. My first question is that while using SSE i observed that the client keeps making a request to the server and if data is available it pulls it. Its similar to an Ajax call being sent every 3-4 seconds which can be changed but what i really want is that only and only when the Data in the DataBase changes should there be a refresh in the DataTable. Also i want to send JSON data to the client but am unable to send it in the right format. Below is my controller code.
def test(){
def action
something.each(){
action = "<a href=\"javascript:fetchDetails('"+it.id+"','comments'"+")\" class='btn btn-primary'><span class='glyphicon glyphicon-upload'></span></a>"
dataArr << [
it.Number,
it.product,
it.description,
OrgChart.findByid(it.Owner)?.displayName,
OrgChart.findByid(it.Coordinator)?.displayName,
startDate,
endDate,
it.status.status,
action
]
}
println dataArr
response.setContentType("text/event-stream;charset=UTF-8")
response << "data: ${dataArr}\n\n"
render "Hi"
}
}
Below is the gsp or the client side code
console.log("Starting eventSource");
var eventSource = new EventSource("/ops/test");
console.log("Started eventSource");
eventSource.onmessage = function(event) {
var data = JSON.stringify(event.data)
console.log("Message received: " + JSON.parse(data));
changeRequestsTable.clear().rows.add(JSON.parse(event.data)).draw()
};
eventSource.onopen = function(event) { console.log("Open " + event); };
eventSource.onerror = function(event) { console.log("Error " + event); };
console.log("eventState: " + eventSource.readyState);
// Stop trying after 10 seconds of errors
setTimeout(function() {eventSource.close();}, 10000);
I know i am a long way from implementing what i intend to but any help would be really appreciated

Going to answer this since it is getting to be a long conversation. As it stands the solution is too broad to give a proper answer since the angle as to how you do things could vary in such a dramatic range from using events that get triggered upon record save that then go off to either make client socket connections through application through to direct socket client connection at point of save that triggers something to be sent to clients. These methods are probably all more complex and more entangled and in short can be done all in a much easier way.
As the users go their interface get the users to make a ws connection to a backend listener. It can be the same location as in no room/separation (additional complexity needed).
As they join room declare a static concurrent map in the top of your websocket listener that collections each session and userId. I wouldn't do it the chat way since this is injected through a service that keeps it as a collection instead like this and changing RunnableFuture to be Websocket sessions like seen in the service link example.
Once you have this you can simply call a broadcast something like this that gets hold of your static concurrent map and for each session either broadcasts the entire new list in json and user processes html update with it or sends a trigger to say update page and they go off doing ajax call to update list.

See the following guide for a tutorial on how to implement Server Sent Events with Grails 3:
http://guides.grails.org/server-sent-events/guide/index.html

Cognito Identity returning the same ID every time - Node JS

I am trying to obtain a new Cognito Identity during the user signup process. Here's a code snippet:
aws.config.credentials = new aws.CognitoIdentityCredentials(unauthCred);
aws.config.credentials.get(function(err) {
var id = aws.config.credentials.identityId;
}
I am expecting this to give me a new unique id every call. However, I am getting the same id every time. Is this the expected behavior? What can I do to get the behavior I want?

The identityId is cached, so you would get a new identityId if you clear the cached one, or call GetId API.
P.S.: Cognito Identity Credentials are not really suited for a server side use case. Can you please elaborate your use case, so that we can help you in a better manner?
-Rachit

save passwords for my website using JavaScript

Rigth now i'm creating my own website and there need to be a log in function. I've made a sign up page that retrieves data from the input fields and now comes the problem. I don't know how to save the passwords and username etc. Is it possible to save this into a text file and every time i open the website it retrieves this data? So, yes how do i do this and if this can't is there another way?
Here you see the code it retrieves. These variables need to be safed in a text file and retrieved next time website will be opend
var voornaam = document.getElementById("voorn").value;
var achternaam = document.getElementById("achtern").value;
var mail = document.getElementById("mail").value;
var password = document.getElementById("pass").value;
var gender = document.getElementById("iGender").value;
Solution:
Use a Database to save this information. Here a some Databases Mongo DB and Firebase
https://www.firebase.com/
Here's a course for Firebase http://www.codecademy.com/en/tracks/firebase

In addition to hashing the password, you probably want to be storing this information in a database. You will then have to add some logic to your application so that when a user logs in to your website, the values they enter into the log in form are checked against the values stored in the database when they signed up. In very general terms, that is probably the most standard architecture to get a log in functionality up and running.

You will have to write a service on your server that takes the form values, checks them against a database and then updates the HTML accordingly.

You could create a cookie and read it when the page loads: http://www.w3schools.com/js/js_cookies.asp
Create: document.cookie = "voornaam="+voornaam
Read: $(function(){ voornaam = document.cookie.replace("voornaam=",""); })
EDIT:
To save objects, you can use the JSON-library like so:
document.cookie = JSON.stringify({foo:"bar"}); cookieObject = JSON.parse(document.cookie);
But have in mind that the user can read and manipulate this cookie...

Node.JS Socket.IO sending packets to specific connection IDs

I have been searching for this particular problem for the past week, and since I couldn't find any information on the subject(that wasnt outdated), I just decided to work on other things. But now I am at the point where I need to be able to send data(that I constructed) to specific clients using their ID who are connected to my server using node.js and socket.io. I already store the ID in an object for each new connection. What I need to know is a way to just send it to a connection ID I choose.
Something like: function send(data, client.id) {};
I am using an http server, not TCP.
Is this possible?
edit:
server = http_socket.createServer(function (req, res) {
res.writeHead(200, {'Content-Type': 'text/html'});
res.end(respcont);
client_ip_address = req.header('x-forwarded-for');
});
socket = io.listen(1337); // listen
//=============================================
// Socket event loop
//=============================================
socket.on ('connection', function (client_connect) {
var client_info = new client_connection_info(); // this just holds information
client_info.addNode(client_connect.id, client_connect.remoteAddress, 1); // 1 = trying to connet
var a = client_info.getNode(client_connect.id,null,null).socket_id; // an object holding the information. this function just gets the socket_id
client_connect.socket(a).emit('message', 'hi');
client_connect.on('message', function (data) {
});
client_connect.on ('disconnect', function () {
);
});
solution: I figured it out by just experimenting... What you have todo is make sure you store the SOCKET, not the socket.id (like i was doing) and use that instead.
client_info.addNode(client_connect.id, client_connect.remoteAddress, client_connect, 1)
var a = client_info.getNode(client_connect.id,null,null,null).socket;
a.emit('message', 'hi');

If you need to do this, the easiest thing to do is to build and maintain a global associative array that maps ids to connections: you can then look up the appropriate connection whenever you need and just use the regular send functions. You'll need some logic to remove connections from the array, but that shouldn't be too painful.

Yes, it is possible.
io.sockets.socket(id).emit('message', 'data');

Your solution has one major drawback: scaling. What will you do when your app needs more the one machine? Using internal IDs also could be difficult. I advice using external IDs (like usernames).
Similarly to this post I advice using rooms (together with Redis to allow scaling). Add private room for every new socket (basing on user's name for example). The code may look like this:
socket.join('priv/' + name);
io.sockets.in('priv/' + name).emit('message', { msg: 'hello world!' });
This solution allows multiple machines to emit events to any user. Also it is quite simple and elegant in my opinion.