How to Export Socket.Io into Other Modules in Nodejs

How can i export socket.io into other modules in nodejs?

Since app.js is usually kind of the main initialization module in your app, it will typically both initialize the web server and socket.io and will load other things that are needed by the app.

As such a typical way to share io with other modules is by passing them to the other modules in that module's constructor function. That would work like this:

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

// load consumer.js and pass it the socket.io object
require('./consumer.js')(io);

// other app.js code follows

Then, in consumer.js:

// define constructor function that gets `io` send to it
module.exports = function(io) {
    io.on('connection', function(socket) {
        socket.on('message', function(message) {
            logger.log('info',message.value);
            socket.emit('ditConsumer',message.value);
            console.log('from console',message.value);
        });
    });
};

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Or, if you want to use a .start() method to initialize things, you can do the same thing with that (minor differences):

// app.js
var server = require('http').createServer(app);
var io = require('socket.io')(server);

// load consumer.js and pass it the socket.io object
var consumer = require('./consumer.js');
consumer.start(io);

// other app.js code follows

And the start method in consumer.js

// consumer.js
// define start method that gets `io` send to it
module.exports = {
    start: function(io) {
        io.on('connection', function(socket) {
            socket.on('message', function(message) {
                logger.log('info',message.value);
                socket.emit('ditConsumer',message.value);
                console.log('from console',message.value);
            });
        });
    };
}

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This is what is known as the "push" module of resource sharing. The module that is loading you pushes some shared info to you by passing it in the constructor.

There are also "pull" models where the module itself calls a method in some other module to retrieve the shared info (in this case the io object).

Often, either model can be made to work, but usually one or the other will feel more natural given how modules are being loaded and who has the desired information and how you intend for modules to be reused in other circumstances.

How to export Socket.io instance on other files of the project

let yoyo = require('socket.io') This line is requiring, a new, socket.io function.

You're exporting in your server.js, so you should import from that file like:

// assuming the file you're importing from is in the same folder as server.js
let yoyo = require('./server');

How can i share socket.io into other modules in nodejs?

You can export not only the function that initiates the server, but a class that handles all the socket.io connection and functionality. This class will be a singleton and will have functions that uses the connection, and can be usable in the different modules.

example:
app.js:

'use strict'
const express = require('express');

const realtime = require('./controllers/realtime');

const app = express();
const server = require('http').Server(app);

var sessionMiddleware = session(sessionConfig);
realtime.connect(server,sessionMiddleware);

realtime.js:

let connection = null;

class Realtime {
    constructor() {
        this._socket = null;
    }
    connect(server,sessionMiddleware) {
        const io = require('socket.io')(server);

        io.use(function(socket, next) {
            sessionMiddleware(socket.request, socket.request.res, next);
        });
        io.on('connection', (socket) => {
            this._socket = socket; 
            this._socket.on('statusConnetion',(data)=>{
                console.log(data)
            });

            this._socket.on('disconnect', function () {
                console.log(socket.id,"Un socket se desconecto");
            });

            console.log(`New socket connection: ${socket.id}`);
        });
    }

    sendEvent(event, data) {
        this._socket.emit(event, data);
    }

    registerEvent(event, handler) {
        this._socket.on(event, handler);
    }

    static init(server,sessionMiddleware) {
        if(!connection) {
            connection = new Realtime();
            connection.connect(server,sessionMiddleware);
        }
    }

    static getConnection() {
        if(!connection) {
            throw new Error("no active connection");
        }
        return connection;
    }
}

module.exports = {
    connect: Realtime.init,
    connection: Realtime.getConnection 
}

cargos.js:

const express = require('express');
const router = express.Router();

let cargos = {};

cargos.update = (req, res, next) =>{
    const connection  = require('./controllers/realtime').connection();
    connection.sendEvent("update", {params: req.params});
}

module.exports = cargos;

Reference socket.io instance in another file with multiple exports (node.js)

In below code I have exported io object from app.js and you can easily use it where you want

const server = require('http').createServer(app);
const io = require('socket.io')(server, {
  cors: {
    origin: 'http://localhost:8081',
    methods: ['GET', 'POST'],
    allowedHeaders: ['my-custom-header'],
    credentials: true,
  },
});

io.on('connection', async (socket) => {
    console.log('socket connected', userId)

    if (io.nsps['/'].adapter.rooms["room-" + userId] && io.nsps['/'].adapter.rooms["room-" + userId].length > 0) userId++;
    socket.join("room-" + userId);
    io.sockets.in("room-" + userId).emit('connectToRoom', "You are in room no. " + userId);
});

const socketIoObject = io;
module.exports.ioObject = socketIoObject;

where you want to get that function use below code

const socket = require('../app');//import object

socket.ioObject.sockets.in("_room" + room_id).emit("hello", "how are you");

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