UnhandledPromiseRejectionWarning: TypeError: io.emit is not a function

Question

I am using Socket.io for real time image upload process but I got this error mentioned below. I'm writing socket and app.js logics in different files by referring this answer now i want to emit that socket events in controller files but got the error

UnhandledPromiseRejectionWarning: TypeError: io.emit is not a function

below is my code

app.js

 // modules =================================================
 var express = require('express');
 var app = express();
 const logger = require('morgan');
 var bodyParser = require('body-parser');
 const indexRouter = require("./routes/index");
 const cors = require('cors');
 const path = require("path");
 const config = require("./environments/index");
 var http = require('http').Server(app);
 var sockets = require('./apis/socket.io');
 // configuration ===========================================
 var port = config.PORT || 8081; // set our port

 sockets.getSocketIo(http);

 app.use(bodyParser.json({ limit: '50mb' }));

 app.use(bodyParser.urlencoded({
    limit: '50mb',
    extended: true,
    parameterLimit: 50000
 }));
 app.use(cors());
 app.use(logger('dev'))
 app.use("/api", indexRouter);

 app.use(express.static(path.join(__dirname, "/build")));

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

  http.listen(port, () => {
      console.log('Magic happens on port ' + port); // shoutout to the user
  });

 exports = module.exports = app;

This is socket.io.js file code

 var socketio = require('socket.io');
 var io = {};

 module.exports = {

getSocketIo: function (app) {

    let userId = 1

    io = socketio.listen(app);
    io.sockets.on('connection', function (socket) {
        console.log("new connection: " + socket.id);

        console.log(socket)


        console.log('socket connected')

        // let rooms = socket.id


        io.sockets.adapter.rooms
        if (io.nsps['/'].adapter.rooms["room-" + userId] && io.nsps['/'].adapter.rooms["room-" + 
  userId].length > 0) userId++;
        socket.join("room-" + userId);

        //Send this event to everyone in the room.
        io.sockets.in("room-" + userId).emit('connectToRoom', "You are in room no. " + userId);
        io.sockets.in(userId).emit('Image_upload', "Image uploading is started");
        console.log(socket.room)
        console.log(socket)
    });
}
};

This is controller code of api controller

 report_data: async (req, res) => {
    if (!req.body.id) {
        logger.warn(error.MANDATORY_FIELDS);
        return res.status(500).send(error.MANDATORY_FIELDS)
    }
    io.emit('progress', "Image is Uploading started Please Wait A minute");
    io.emit('error', "clients connected!");

    let Id = req.body.id;
    let path = `tmp/daily_gasoline_report/${Id}`;

    req.body.data_url = path
    sequelize.sequelize.transaction(async (t1) => {
        let result = error.OK
        result.data = data

        logger.info(result);
        return res.status(200).send(result)
    }).catch(function (err) {
        logger.warn(err);
        console.log(err)
        return res.status(500).send(error.SERVER_ERROR)
    })
},

Answer 1

You can Make changes like below in your file

app.js

// modules =================================================
var express = require('express');
var app = express();
const logger = require('morgan');
var bodyParser = require('body-parser');
const cors = require('cors');
const path = require("path");
const config = require("./environments/index");
var http = require('http').Server(app);
var io = require('socket.io').listen(http);
const indexRouter = require("./routes/index");

// configuration ===========================================
var port = config.PORT || 8081; // set our port

app.use(bodyParser.json({ limit: '50mb' }));

app.use(bodyParser.urlencoded({
    limit: '50mb',
    extended: true,
    parameterLimit: 50000
}));
app.use(cors());
app.use(logger('dev'))
app.use("/api", indexRouter);

app.use(express.static(path.join(__dirname, "/build")));

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

http.listen(port, () => {
    console.log('Magic happens on port ' + port); // shoutout to the user
});

app.locals.io = io

exports = module.exports = app;

socket.io.js

let io;

const getSocketIo = (http) => {
    let userId = 1

    io = require('socket.io')(http);
    io.sockets.on('connection', function (socket) {

        io.sockets.adapter.rooms
        if (io.nsps['/'].adapter.rooms["room-" + userId] && io.nsps['/'].adapter.rooms["room-" + userId].length > 0) userId++;
        socket.join("room-" + userId);

        //Send this event to everyone in the room.
        io.sockets.in("room-" + userId).emit('connectToRoom', "You are in room no. " + userId);
        console.log("new connection: " + socket.id);
        console.log('socket connected')
    });
}

module.exports = {
    getSocketIo,
    io
};

in your controllers add this code in api you have mentioned whenever you want to use socket add this code before using it

const io = req.app.locals.io;