Challenge:
I would like to use SailsJS, and be able to join a room, by means of socket.io, and receive unsolicited messages from this room, not just when one enters or leaves the room but also receive objects.
So several clients connect to the server.
Afterwards broadcast (initiated from the server) messages/objects to every room and thus everey connected socket in this room.
I maybe could just send every connected socket a message, but dearly would like a example on how to do this with SailsJS 0.10, and a elegant method in the SailsJS 0.10 way.
I am looking at : https://github.com/balderdashy/sailsChat, but I think this is to close to the models themselves, with like e.g: autosubscribe: ['destroy', 'update']
In my opinion this should be more loosely coupled, and not so tied to the model itself.
Thanks in advance!
I.
The purpose of the SailsChat example is to demonstrate how Sails JS resourceful pubsub can take a lot of hassle out of socket messaging when you are mainly concerned with sending messages about models. The fact that you can make a full-featured chat app in Sails with very little back-end code is what makes it impressive. For situations where resourceful pubsub is not appropriate--or if you just plain don't want to use it--Sails exposes lower-level methods on the sails.sockets namespace. The docs are pretty clear on how they work.
To join a socket to an arbitrary room, do sails.sockets.join(<socket>, <roomName>), where <socket> is either a raw socket (probably from req.socket or a socket ID).
To broadcast a message to all sockets in a room, do sails.sockets.broadcast(<roomName>, <data>).
These and more methods are described in detail in the Sails JS documentation.
I'm just starting with SailsJS, and already a big fan.
I need to find out if this is also scalable with e.g. Heroku or other flavors of SAAS providers, but seems not that hard.
So just a follow up on what I did with SailsJS 0.10:
Server-side:
Made a controller with the following:
join: function (req, res) {
if (req.isSocket === true) {
sails.sockets.join(req.socket, 'mysecretroom');
return res.send(200, 'joined');
}
return res.send(200);
},
sendToRoom: function( req, res ) {
if (req.isSocket === true ) {
sails.sockets.broadcast('mysecretroom', 'messageevent', {message:'Listen very carefully, I'll shall say this only once..!'});
}
return res.send(200);
}
Client-side:
io.socket.on('messageevent', function (data) {
console.log(data);
})
+1 kudos #sgress454!
Thanks!
Related
First of all I'm an OG bare metal Java server side guy. That means I'm new to Docker, Node.js (JavaScript in general), socket.io and trying to learn all these things at once so please pardon me if I've made an obvious mistake. I've been working on a pro-bono project for some time in hope that in exchange I get to learn all of these things and move into the new way of doing things.
Now, having said that, moving along to my question - In the code snippet below (especially the last line)
io.on('connection', function (socket) {
console.log(`connection made from ${socket.id}`);
socket.on('disconnect', function () {
console.log(`connection ${socket.id} closed`);
});
socket.on(DOWNSTREAM_MESSAGE, function (msg) {
//console.log(`Received socket payload: ${msg} from ${socket.id}`);
iopubClient.publish(DOWNSTREAM_MESSAGE, msg);
});
iosubClient.subscribe(UPSTREAM_MESSAGE, message => {
//console.log(`Sending socket payload: ${message} to ${socket.id}`);
socket.emit(UPSTREAM_MESSAGE, message);
});
});
as far as I understand from all the internet sleuthing is that:
io.emit(....
broadcasts to all clients the server socket is connected to, and
socket.emit(....
sends to the call initiator (specifically referring to emit cheat sheet among other sources).
However, with the code snippet above, even when I'm using socket.emit, all subscribing socket.io clients receive the message as if it were a broadcast which isn't what I want. I really do want to send the response back to the io that initiated this particular request.
I've tried almost every way of achieving session stickiness from session stickiness (current implementation an attempt via cookie based stickiness with a HAProxy in front of the service).
In case it helps you help me, full code-base is here.
As I mentioned, I'm learning all of this on the fly so I will not be embarrassed (in fact would be quite thankful!) if you point me to something I'm doing wrong, but for the life of me, I cannot get the response to go only to the request initiator.
Please help?!
I'm new to websockets/socket.io/node.js. I'm trying to write a card game app, but pretty much all the example tutorials I've found are creating chat applications. So I'm struggling to get my head around the concepts and how they can be applied to my card game.
Keeping it simple, the card game will involve two players. The game involves moving cards around the table. Each player has to see the other player's moves as they happen (hence the need for constant connections). But the opponents cards are concealed to the other.
So two people browse to the same table then click to sit (and play, when both seats are taken). Using
io.on("connection", function(sock){
//socket events in here
});
am I creating the one socket ('io', or 'sock'?) that both clients and the server share, or is that two separate sockets (server/clientA and sever/clientB)? I ask, because I'm struggling to understand what's happening when a message is emitted and/or broadcast. If a client emits a message, is that message sent to both the server and the other client, or just the server? And then, further does it also send the message to itself as well?? It seems as though that's the logic... or what is the purpose of the 'broadcast' method?
From a functional perspective, I need the server to send different messages to each player. So it's not like a chatroom where the server sends the chat to everyone. But if it's one socket that the three of us share (clients and server), how do I manage who sees what? I've read about namespaces, but I'm struggling to work out how that could be used. And if it's two separate sockets, then I can more easily imagine sending different data to the separate clients. But how is that implemented - is that two 'io' objects, or two 'sock' objects?
Finally, I've got no idea if this is the sort of long-winded question that is accepted here, so if it's not, can someone direct me to a forum that discussions can occur? Cheers!
(in case it matters I'm also using Expressjs as the server).
Edit to add:
Part of my confusion is regarding the difference between 'io' and 'sock'. This code eg from the socket.io page is a good example of methods being applied to either of them:
io.on('connection', function(socket){
socket.emit('request', /* */); // emit an event to the socket
io.emit('broadcast', /* */); // emit an event to all connected sockets
socket.on('reply', function(){ /* */ }); // listen to the event
});
WebSocket server side listens for incoming socket connections from clients.
Each client upon connection opens its own socket between him and server. The server is the one that keeps track of all clients.
So once client emits the message server is listening for, the server can do with that message whatever. The message itself can contain information about who is the recipient of that message.
The server can pass the message to everyone or broadcast it to specific user or users based on information your client has sent you or some other logic.
For a card game:
The server listens for incoming connections. Once two clients are connected both of them should emit game ID in which they want to participate. The server can join their sockets in one game(Room) and all of the communication between those two clients can continue in that room. Each time one of the clients passes data to the server, that data should contain info about the recipient.
Here is one simple example that could maybe get you going:
Client side
// set-up a connection between the client and the server
var socket = io.connect();
// get some game identifier
var game = "thebestgameever";
socket.on('connect', function() {
// Let server know which game you want to play
socket.emit('game', game);
});
function makeAMove(move)
{
socket.emit('madeAMove', {move:move, game:game});
}
socket.on('move', function(data) {
console.log('Player made a move', data);
});
Server side
io = socketio.listen(server);
//listen for new connections from clients
io.sockets.on('connection', function(socket) {
// if client joined game get his socket assigned to the game
socket.on('game', function(game) {
socket.join(game);
});
socket.on('madeAMove', function(data){
let game = data.game;
let move = data.move;
io.sockets.in(game).emit('move', move);
});
})
I earlier had all my code in socket.io+node.js server. I recently converted all the code to redis+socket.io+socket.io+node.js after noticing slow performance when too many users send messages across the server.
So, why socket.io alone was slow because it is not multi threaded, so it handles one request or emit at a time.
What redis does is distribute these requests or emits across channels. Clients subscribe to different channels, and when a message is published on a channel, all the client subscribed to it receive the message. It does it via this piece of code:
sub.on("message", function (channel, message) {
client.emit("message",message);
});
The client.on('emit',function(){}) takes it from here to publish messages to different channels.
Here is a brief code explaining what i am doing with redis:
io.sockets.on('connection', function (client) {
var pub = redis.createClient();
var sub = redis.createClient();
sub.on("message", function (channel, message) {
client.emit('message',message);
});
client.on("message", function (msg) {
if(msg.type == "chat"){
pub.publish("channel." + msg.tousername,msg.message);
pub.publish("channel." + msg.user,msg.message);
}
else if(msg.type == "setUsername"){
sub.subscribe("channel." +msg.user);
}
});
});
As redis stores the channel information, we can have different servers publish to the same channel.
So, what i dont understand is, if sub.on("message") is getting called every time a request or emit is sent, why is redis supposed to be giving better performance? I suppose even the sub.on("message") method is not multi threaded.
As you might know, Redis allows you to scale with multiple node instances. So the performance actually comes after the fact. Utilizing the Pub/Sub method is not faster. It's technically slower because you have to communicate between Redis for every Pub/Sign signal. The "giving better performance" is only really true when you start to horizontally scale out.
For example, you have one node instance (simple chat room) -- that can handle a maximum of 200 active users. You are not using Redis yet because there is no need. Now, what if you want to have 400 active users? Whilst using your example above, you can now achieve this 400 user mark, which is a "performance increase". In the sense you can now handle more users, but not really a speed increase. If that makes sense. Hope this helps!
I'm writing an application in Node.js/Express based around websockets. I'm using Node's EventEmitter in conjunction with socket.io for a nearly completely event-driven app.
I wonder if this this is a good architecture though. My main socket is managed in app.js right now, and has code like this:
socket.on(Events.InitialFetch, function(battle_id){
dispatcher.emit(Events.InitialFetch, battle_id);
});
dispatcher.on(Events.InitialFetched, function(data){
socket.emit(Events.InitialFetched, data);
});
... while in my controller, I have code like this:
dispatcher.on('initial-fetch', function(data){
Battle.findOne({_id: data})
.populate('players')
.populate('owner')
.exec(function(err, battle){
if (err) {
}
else {
dispatcher.emit(Events.InitialFetched, battle);
}
});
});
Instead of the normal RESTful routing. My concern is that it's a little confusing (ie 'fetch' and 'fetched' for describing data flow) and the fact that I'm basically passing methods from one type of event emitter (socket.io) to another (Event.EventEmitter).
How can this be architected better? Would it be better to have the controllers directly access the socket instead of using EventEmitter as a bus? How can I make the names of my events more clear?
I wouldn't worry about using multiple event emitters. They are kind good primitive to build upon in Node.js. As for design, I find a good question to ask is how deeply I have coupled my components.
By using an non-socket.io event emitter for your controller, Socket.io is an independent transport from the controller. This is good.
As a final stage, you should wire the two together using dependency injection. In your server.js file create your dispatcher, then initialize your socket.io module passing the dispatcher as a dependency.
var dispatcher = require('./dispatcher')
var socket_transport = require('./socket_transport')
socket_transport.init_with_dispatcher(dispatcher);
This will let you test your dispatcher independently of the transport. Debugging socket.io can be difficult.
I'm using Socket.IO in my Node Express app, and using the methods described in this excellent post to relate my socket connections and sessions. In a comment the author describes a way to send messages to a particular user (session) like this:
sio.on('connection', function (socket) {
// do all the session stuff
socket.join(socket.handshake.sessionID);
// socket.io will leave the room upon disconnect
});
app.get('/', function (req, res) {
sio.sockets.in(req.sessionID).send('Man, good to see you back!');
});
Seems like a good idea. However, in my app I will often by sending messages to multiple users at once. I'm wondering about the best way to do this in Socket.IO - essentially I need to send messages to multiple rooms with the best performance possible. Any suggestions?
Two options: use socket.io channels or socket.io namespaces. Both are documented on the socket.io website, but in short:
Using channels:
// all on the server
// on connect or message received
socket.join("channel-name");
socket.broadcast.to("channel-name").emit("message to all other users in channel");
// OR independently
io.sockets.in("channel-name").emit("message to all users in channel");
Using namespaces:
// on the client connect to namespace
io.connect("/chat/channel-name")
// on the server receive connections to namespace as normal
// broadcast to namespace
io.of("/chat/channel-name").emit("message to all users in namespace")
Because socket.io is smart enough to not actually open a second socket for additional namespaces, both methods should be comparable in efficiency.