socket.io emit when someone call the API

Question

I have a small project with NodeJS Express server and Angular2 frontend. The server has an API interfaces. The main part of this is: /api/alert. I want to do the following: If the /api/alert get an request then socket.io broadcast an event to all connected clients.

My server structure is the following:

server.js

var http        = require('http'),
    express     = require('express'),
    app         = module.exports.app = express(),
    port        = process.env.PORT || 3000,
    mongoose    = require('mongoose'),
    bodyParser  = require('body-parser'),
    db          = require('./config/db'),
    path        = require('path');

mongoose.Promise = global.Promise;
mongoose.connect(db.url);

app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

app.use(express.static(path.join(__dirname, 'dist')));

var routes = require('./server/routes/index');
routes(app);

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

console.log('Server started on: ' + port);

server/routes/index.js

const deviceRoute   = require('./devicesRoute');
const alertRoute    = require('./alertsRoute');

module.exports = function(app) {
    deviceRoute(app);
    alertRoute(app);
}

server/routes/alertRoute.js

'use strict';
module.exports = function(app) {

    var alertsService = require('../services/alertsService');

    app.route('/api/alert')
        .post(alertsService.createAlert);
};

server/service/alertService.js

'use strict';

exports.createAlert = function(req, res) {
    // do something in database

    // I want to broadcast to all client HERE
};

I can't pass the io and server variables to the function (from server.js). How can I do that? What is the easiest way?

Thank you!

Answer 1

First you would want to export both the app and server objects from server.js and pass your socket to your response in middleware as follows:

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

app.use(function(req, res, next){
    res.io = io;
    next();
});

...

module.exports = {app: app, server: server};

You can then require the server instance you created in server.js (depending on where you are requiring it from) as

var server = require('../server').server;

Since you added socket.io to the response object, you can use it in your services as

'use strict';

exports.createAlert = function(req, res) {
    // do something in database

    // I want to broadcast to all client HERE
    res.io.emit("broadcast", "clients");

};