socket.io - ReferenceError: io is not defined

user_1353951 0
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I am writing an application for Android 2.3.5 (that will also be compatible with iOS). I wish to transfer data from the app's HTML/Javascript to a Python program on a server (which uses the Twisted engine to retrieve the data).

I've tried many things and looked at various forums, answers, tutorials, and web pages--including most of them here--and can't find an answer. Here's the relevant Javascript I have in my index.html file:

<script src="socket-lib/socket.io.js"></script>
<script type="text/javascript" charset="utf-8">
function sendData() {
    try {
        var socket = io.connect('http://mywebsite.com:12345');
        socket.on('connect', function(data) {
            socket.send('Hello.');
            socket.on('message', function (msg) {
                socket.send('This is where I send data?');
            });
        });
    }
    catch(err) {
        alert('ERROR: socket.io encountered a problem:\n\n' + err);
    }
} // end of sendData

If you can't tell, I'm still pretty confused how this works; I can't even test anything. The error that keeps coming up is ReferenceError: io is not defined. Some sites used something like var io = require('socket.io');. But then it results in the same error: ReferenceError: require is not defined.

I put the socket-lib folder in assets/www, where any other Javascript source should go. This is also where the index.html file is. Many sites use <script src="/socket.io/socket.io.js"></script>, but this makes no sense to me. Many sites also imply the use of node.js, but I never see it anywhere.

How can I make this work?

Reply edits:

I tried it in Chrome, and it's giving me an Uncaught ReferenceError: require is not defined for the socket.io.js file. So I decide to source in require.js right before it. Then it gives the error Uncaught Error: Module name "socket.io-client" has not been loaded yet for context. Since I'm not using this, I care not. When I try the connection, though, it gives the same io is not defined error. When I define it as var io = require('socket.io'), the error is Error: Module name "socket.io" has not been loaded yet for context: _ http://requirejs.org/docs/errors.html#notloaded. I looked at the website, and it doesn't help me at all. When I try to put "require" as a function argument, another error occurs: TypeError: undefined is not a function.

referenceerror socket.io android javascript ios
11 Answers

write server side code in socket.io.js file and try src="/socket.io/socket.io.js"

hope this will solve your problem

user_91169950

In my case, using Unity WebGL with C# UnitySocketIO plugin, I need to add delay (1 sec) between Init and Connect, because the first method did not have time to add a new JS Socket object and code (listeners) to the page to work with it..

user_23073670

As mentioned in other answers, you have to use the complete URL.

<script src="http://127.0.0.1:5565/socket.io/socket.io.js "></script>

if it's giving you an error 404 please check whether io is properly instantiated on your server.js.If not please refer following to instantiate the io properly.

<script>
  var socket = io();
</script>

In your server.js

const app = express();
const http = require('http'); //from express module
const server = http.createServer(app);
const { Server } = require("socket.io");
const io = new Server(server);
user_113043520

got to url /socket.io/socket.io.js and check if a js file is served or not if yes then instead of writing

var socket = io();

write

window.onload= function(){
var socket = io();
}
user_182850420
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