Raspberry Pi Forums

Posted: **Fri Jul 28, 2017 5:49 am**

I'm trying to get this up and running and the NodeJS seems to be fine, my problem is my HTML page can't find the socket.io/socket.io.js

Here is my server code:

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var express = require('express');
var app = express();
var server = require('socket.io');
app.use(express.static('public'));
server.createServer(app).listen(8080);

var serv_io = io.listen(server);
serv_io.sockets.on('connection', function(socket) {
console.log('user connected');
socket.emit('SocketCallback', {value:'Connection Successful'});
});

and my html

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<head>
<script src="/socket.io/socket.io.js"></script>
</head>
<body>
<script type="text/javascript">
var socket = io();
socket.on('SocketCallback', function (data) {
console.log(data);
});
</script>
</body>

Now here is my file structure:

project-folder/index.js
project-folder/package.json
project-folder/node_modules
project-folder/public/index.html

When I run the index.js the server seems fine and no issues, when I open the index.html page in the browser on the pi it can't find the socket.io.js file and because of that io is undefined.

Can anyone please offer some help?

Posted: **Fri Jul 28, 2017 5:56 pm**

Looks like your server is listening on port 8080.

Meanwhile the JS in your page might not be requesting from that port.

The simple socket.io with express example on the socket.io web site works fine. https://socket.io/docs/
Or at least my rendition of it does, see below.

Also you have no connect call in your client side JS. Like so:

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var socket = io.connect();

or

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var socket = io.connect('whateverurl:whateverport');

index.js:

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var app = require('express')();
var server = require('http').Server(app);
var io = require('socket.io')(server);

server.listen(8080);

app.get('/', function (req, res) {
    res.sendfile(__dirname + '/index.html');
});

io.on('connection', function (socket) {
    socket.emit('news', { hello: 'world' });
    socket.on('my other event', function (data) {
        console.log(data);
    });
});

index.html:

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<html>
    <head>
        <script src="/socket.io/socket.io.js"></script>
    </head>
    <body>
        <h1>Hello!</h1>
        <script type="text/javascript">
            var socket = io.connect('http://localhost:8080');
            socket.on('news', function (data) {
                console.log(data);
                socket.emit('my other event', { my: 'data' });
            });
        </script>
    </body>
<html>

Posted: **Fri Jul 28, 2017 9:14 pm**

Thanks for the feed back Heater.

I've tried so much and with it being late yesterday I don't even remember what I did and didn't do.

Today I have the following:

index.js:

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var app = require('express')();
var server = require('http').Server(app);
var io = require('socket.io')(server);

server.listen(8080);

app.get('/', function (req, res) {
   res.sendfile(__dirname + '/manual.html');
});

function onConnection(socket) {
  console.log('user connected');
  socket.emit('notify', { value: '...is this thing on?' });
}

io.on('connection', onConnection);

manual.html

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<!DOCTYPE html>
<html lang="en">
<html>
    <head>
        <meta charset="UTF-8">
        <title> ... Testing ... </title>
        <link rel="shortcut icon" href="favicon.ico" type="image/x-icon">
        <link rel="icon" href="favicon.ico" type="image/x-icon">
        <link rel="stylesheet" type="text/css" href="web.css">
	<script src="/socket.io/socket.io.js"></script>
    </head>

    <body>
	<script type="text/javascript">
		var socket = io.connect(); // i have tried var socket = io.connect('http://localhost:8080');
		socket.on('notify', function ( data ) {
			console.log(data);
		});
	</script>
    </body>
</html>

When I run

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node index.js

I get the following error:

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/home/pi/node_programs/deserest/node_modules/socket.io/node_modules/engine.io/node_modules/ws/index.js:9
const WebSocket = require('./lib/WebSocket');
^^^^^
SyntaxError: Use of const in strict mode.
    at exports.runInThisContext (vm.js:73:16)
    at Module._compile (module.js:443:25)
    at Object.Module._extensions..js (module.js:478:10)
    at Module.load (module.js:355:32)
    at Function.Module._load (module.js:310:12)
    at Module.require (module.js:365:17)
    at require (module.js:384:17)
    at Server.init (/home/pi/node_programs/deserest/node_modules/socket.io/node_modules/engine.io/lib/server.js:119:16)
    at new Server (/home/pi/node_programs/deserest/node_modules/socket.io/node_modules/engine.io/lib/server.js:65:8)
    at Function.attach (/home/pi/node_programs/deserest/node_modules/socket.io/node_modules/engine.io/lib/engine.io.js:123:16)

Even better if I clone done an example project I get the same issue.
I know there's something I'm overlooking I'm just past being tired and am not seeing the issue.

Posted: **Fri Jul 28, 2017 9:30 pm**

Well, it was something sill.
It never crossed my mind to check the version of node that was installed.

Turns out it was version 0.12, I have upgraded the installed version and I'm able to connect.

Posted: **Sat Jul 29, 2017 1:16 am**

Excellent.

Yes, version 0.12... is ancient in the node.js world. A lot has change since then. For example "const" is a language feature of the new 2015 standard of Javascript.

I use nvm to make it easy to install new versions of node. Or revert back to older versions should anything break.

https://github.com/creationix/nvm

I have also taken to getting my node programs to test the version of node they are running under and refuse to start, with a polite message, if the version is older than what I originally wrote the program with.

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