Develop Reference

WebSocket needs browser refresh to update list

My project works as intended except that I have to refresh the browser every time my keyword list sends something to it to display. I assume it's my inexperience with Expressjs and not creating the route correctly within my websocket? Any help would be appreciated.
Browser
let socket = new WebSocket("ws://localhost:3000");
socket.addEventListener('open', function (event) {
console.log('Connected to WS server')
socket.send('Hello Server!');
});
socket.addEventListener('message', function (e) {
const keywordsList = JSON.parse(e.data);
console.log("Received: '" + e.data + "'");
document.getElementById("keywordsList").innerHTML = e.data;
});
socket.onclose = function(code, reason) {
console.log(code, reason, 'disconnected');
}
socket.onerror = error => {
console.error('failed to connect', error);
};
Server
const ws = require('ws');
const express = require('express');
const keywordsList = require('./app');
const app = express();
const port = 3000;
const wsServer = new ws.Server({ noServer: true });
wsServer.on('connection', function connection(socket) {
socket.send(JSON.stringify(keywordsList));
socket.on('message', message => console.log(message));
});
// `server` is a vanilla Node.js HTTP server, so use
// the same ws upgrade process described here:
// https://www.npmjs.com/package/ws#multiple-servers-sharing-a-single-https-server
const server = app.listen(3000);
server.on('upgrade', (request, socket, head) => {
wsServer.handleUpgrade(request, socket, head, socket => {
wsServer.emit('connection', socket, request);
});
});

In answer to "How to Send and/or Stream array data that is being continually updated to a client" as arrived at in comment.
A possible solution using WebSockets may be to
Create an interface on the server for array updates (if you haven't already) that isolates the array object from arbitrary outside modification and supports a callback when updates are made.
Determine the latency allowed for multiple updates to occur without being pushed. The latency should allow reasonable time for previous network traffic to complete without overloading bandwidth unnecessarily.
When an array update occurs, start a timer if not already running for the latency period .
On timer expiry JSON.stringify the array (to take a snapshot), clear the timer running status, and message the client with the JSON text.
A slightly more complicated method to avoid delaying all push operations would be to immediately push single updates unless they occur within a guard period after the most recent push operation. A timer could then push modifications made during the guard period at the end of the guard period.
Broadcasting
The WebSockets API does not directly support broadcasting the same data to multiple clients. Refer to Server Broadcast in ws documentation for an example of sending data to all connected clients using a forEach loop.
Client side listener
In the client-side message listener
document.getElementById("keywordsList").innerHTML = e.data;
would be better as
document.getElementById("keywordsList").textContent = keywordList;
to both present keywords after decoding from JSON and prevent them ever being treated as HTML.

So I finally figured out what I wanted to accomplish. It sounds straight forward after I learned enough and thought about how to structure the back end of my project.
If you have two websockets running and one needs information from the other, you cannot run them side by side. You need to have one encapsulate the other and then call the websocket INSIDE of the other websocket. This can easily cause problems down the road for other projects since now you have one websocket that won't fire until the other is run but for my project it makes perfect sense since it is locally run and needs all the parts working 100 percent in order to be effective. It took me a long time to understand how to structure the code as such.

websocket connection closes upon writing to file

so i am connecting a client to a server using websockets (ws). i successfully send msgs to the server and send it back to the client.Problem is when I try to write the received message to a file the server disconnects the client. The message is successfully written but i end up disconnecting client. Looks like something about the write functions disconnect my client. I am using fs.writFile(), I already tried fs.createWriteStream(). Reading the file however does not disconnect it.
const http = require('http');
const WebSocket = require('ws')
const fs = require('fs');
let counts = [0,0]
const server = http.createServer((req,res)=>{
console.log(' Received request for ' + request.url);
});
const wss = new WebSocket.Server({ port: 8080 });
wss.on('connection',(ws)=>{
console.log("serving...")
ws.on('message',(message)=>{
console.log("Received:"+message)
if(message ==='1'){
counts[0]=parseInt(counts[0])+1
fs.writeFile('votecnts.txt',`${counts[0].toString()} ${counts[1].toString()}`,(err) =>{
if(err) throw err
})
}
else if (message==='2'){
counts[1]=parseInt(counts[1])+1
fs.writeFile('votecnts.txt',`${counts[0].toString()} ${counts[1].toString()}`,(err) =>{
if(err) throw err
})
}
else{console.log(typeof(message))}
ws.send("cand_one: "+counts[0].toString()+"\n cand_two: "+counts[1].toString())
})
ws.on('close',function(){
console.log("lost client")
})
})

So I figured it out. I was running both server and client on localhost while developing. And therefore the file directories are the same. I later found out that it is impossible to write to file in javascript at the client side because of security reasons. So all I did was to change the url of the server to a remote machine and I was able to write to file using server code. specifically with the writeFile() function in the code above. I actually did not have to touch my code. It was just about configuration and set up.

Socket.io and Express not sending data

I'm trying to use socket.io to connect to this websocket api:
https://www.cryptocompare.com/api/#-api-web-socket-
(wss://streamer.cryptocompare.com)
I guess im not really understanding socket.io very much.
I created a blank html document:
<!doctype html>
<html lang="en">
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.1.1/socket.io.slim.js"></script>
</head>
<body>
<div id="data-show">
</div>
<button id="connect-sock">Connect</button>
<button id="disconnect-sock">DISConnect</button>
</body>
<script src="index.js"></script>
</html>
index.js:
var socket = io('wss://streamer.cryptocompare.com')
console.log('connected')
var btn = document.getElementById('connect-sock')
var btn2 = document.getElementById('disconnect-sock')
var show = document.getElementById('data-show')
//I also tried adding an event listener to a button so when i clicked it, it would do this:
socket.emit('SubAdd', { subs: ['0~Poloniex~BTC~USD'] } )
//Same result of nothing.
socket.on('SubAdd', function(data){
console.log(data)
})
server.js:
var express = require('express')
var socket = require('socket.io')
var app = express()
var server = app.listen(4000, function(){
console.log("well met")
})
app.use(express.static('public'))
var io = socket(server)
io.on('connection', function(socket){
console.log('well met from socket connection', socket.id)
})
server.js is in a file named 'socket-test'. index.html and index.js are in 'socket-test/public/'
so for some reason, in server.js, socket.id will not log to console. its as if this function is being skipped over. but when i change the address in index.js to http://localhost:4000, i get socket.id in console... not sure whats going on there.
Edit: I rarely get socket id when using the wss://streamer.cryptocompare.com/ , sometimes I do, most of the time i dont. It usually works when I switch to localhost, run the server, stop the server, then switch back to the streamer, but if i reload, i dont get socket.id anymore.
I thought that all I was asking it to do here was emit subs to wss://streamer.cryptocompare then console.log(data) that it returns after emitting the subs.
am I missing something here?
Sorry in advance if its blatantly obvious that I'm missing something. I've only known about socket.io for maybe 3 days now, and only today have I watched a basic tutorial on youtube.

You don't need the Express code because in this case the server you want to talk to is on the cryptocompare server -- not a local server. This is captured in your code when you initialize the io object in the HTML file.
Of course, you could still use Node to talk to the cryptocompare websockets API if you're more comfortable with Node. But then you wouldn't need the in-browser JavaScript. Either way, what you need is to create some kind of client in any runtime that speaks websockets and can talk to the cryptocompare websockets API.
With regard to the code being skipped over -- you're right! It is. socket.io is an event driven WebSockets framework. This means that clients register their interest in certain kinds of events/messages, and when those are triggered special functions known as callbacks are called.
If it helps, you can think of those events like channels in a chat room -- if you're not in the right room, you won't see the messages for that room. So you'll need to know what messages you should be listening for, register your interest in those, and register callback functions for each one.
Thankfully cryptocompare has provided client code examples that should help you get an idea for the kinds of messages you should be listening for.
See here

Is it possible to create a "fake" socket connection to a nodejs server that is secured through SSL?

I'm using socket.io-client to create a socket connection to my locally-running server. See my code below:
// Working example of connecting to a local server that is not SSL protected
var io = require('socket.io-client')
var socket = io.connect('http://localhost:3000', {reconnect: true});
socket.on('connect', function(){ console.log("inside 'connect'") } );
socket.on('connection', function(){ console.log("inside 'connection'") } );
socket.on('event', function(data){ console.log("inside 'event'") } );
socket.on('disconnect', function(){ console.log("inside 'disconnect'") } );
var payload = {email: 'fake#gmail.com', password: 'tester'};
var tokens = {browserId: 'b965e554-b4d2-5d53-fd69-b2ca5483537a'};
socket.emit("publish", {logic:"user", method:"signIn"}, payload, tokens, function(err, creds) {
console.log("inside the socket client emit callback. err: " + err);
console.log("creds: " + creds);
});
Now for my problem. As I stated in the comment at the top of that code, I can connect to my local nodejs server and get the response I expect when I turn off SSL encryption on my server. As soon as I turn SSL on, I stop getting any response at all from the code above. I don't see any message in my server logs or from the command line, where I'm running the code above with node.
My goal is to be able to run the code above, with SSL turned on in my server, and get the same response that I get when SSL is turned off. I've tried a bunch of variations on the code I included above, such as:
connecting to "https://localhost:3000"
connecting to "//localhost:3000"
connecting to "https://localhost:3443" (this is the port I have to connect to when I have the nodejs server running with SSL)
changing {reconnect:true} to {reconnect:true,secure:true}
I'm truly stumped, and I've been doing a bunch of research on the web and on my node server. It's my company's code and I didn't originally implement the SSL components, so I've spent a few hours looking at our code and trying to understand how adding SSL changes everything. I'm also a student and have about 2 years of experience behind me, so I'm good but I'm no expert. Have I said anything above that indicates if my task is impossible to achieve, or if maybe I have just overlooked something? Any leads on things to check out would be appreciated :)

Can't send message to only one specific room through node.js and socket.io

I have a problem that i don't seems to be able to solve it. I'm doing some kind of integration with remote system and my code is in iframe but that can't be important for this one i hope :).
I'm trying to send a message from server to specific room/client to begin session. First thing I do is when user log in, I emit message from client side with username.
CLIENT.JS
conn.on('connect', function () {
conn.emit('session', { username: 'some_username' });
}, false);
And on server side i get message and join socket to the room.
SERVER.JS
socket.on('session', function(session) {
socket.join(session.username);
});
I have another module that communicates with this server.js script through redis. So i have two more events in server.js
SERVER.JS
var userCreate = redis.createClient();
userCreate.subscribe("userCreate", "userCreate");
var userDestroy = redis.createClient();
userDestroy.subscribe("userDestroy", "userDestroy");
userCreate.on("message", function(channel, data) {
socket.to(JSON.parse(data).username).emit('beginSession', data);
});
userDestroy.on("message", function(channel, data) {
socket.to(JSON.parse(data).username).emit('endSession', data);
socket.leave(JSON.parse(data).username);
});
But when ever i try to emit message from server to client i broadcast message to everyone. What am I doing wrong?

Well, from the syntax point of view you are doing everything correct.
Didn't you forget to specify the userId property in the endSession?
userDestroy.on("message", function(channel, data) {
socket.to(JSON.parse(data).userId).emit('endSession', data);
socket.leave(JSON.parse(data).userId);
});
If that doesn't work - you should provide the contents of a data object