CODEWITHSUNDEEP
javascriptnode.jsexpresswebsocketsocket.io
Ext-
Ext-

Reputation: 531

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.

Upvotes: 0

Views: 666

Answers (1)

Hugo
Hugo

Reputation: 637

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

Upvotes: 2

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