socket emit an event on http PUT - express

Question

I am using expressjs, nedb, and socket.io. Various (non-browser) clients are able to PUT new values into the db successfully. When that happens, I want a message emitted to all browsers connected to the server. I have the following code which is currently not sending a message back to the browser.
// on the server
//***************************************************************
// reachable to the world at http://server/foo
// clients can PUT data into the db
app.put('/foo', jsonParser, function(req, res, next) {
if (!req.body) return res.sendStatus(400);
db.insert(req.body, function (err, newDoc) {
io.sockets.emit('PUT a new value', { added: newDoc._id });
res.send('Success! Find it again with id: ' + newDoc._id);
});
});
// reachable to the world at http://server/
// browser shows a dashboard of events
app.get('/', function(req, res, next) {
// code to serve the dashboard here
});
io.sockets.on('connection', function (socket) {
socket.on('foo', function (data) {
io.sockets.emit('PUT a new value', data);
})
});
// in the browser
//***************************************************************
var socket = io.connect('/');
socket.on('PUT a new value', function (data) {
console.log(data);
});
Data get inserted into the db successfully from different non-browser clients, but the connected browser doesn't receive an update.
What am I doing wrong?

Answer 1

I found a solution which I don't like at all but it works. We can add io object to req or to res in the middleware like that:
app.use(function (req, res, next) {
req.io = io;
next();
});
before app.use('/', routes) and then in our router module we "import" the io object:
app.put('/foo', jsonParser, function(req, res, next) {
if (!req.body) return res.sendStatus(400);
db.insert(req.body, function (err, newDoc) {
var io = req.io; // HERE !!!
io.sockets.emit('PUT a new value', { added: newDoc._id });
res.send('Success! Find it again with id: ' + newDoc._id);
});
});
I know, I know... let's find something else :-)

Answer 2

I have the following app structure generated by express generator. I start the app with $ DEBUG=foo:* npm start
.
|____app.js
|____bin
| |____www
|____data
|____LICENSE
|____node_modules
|____package.json
|____public
| |____stylesheets
| |____javascripts
| |____images
|____README.md
|____routes
| |____index.js
| |____readings.js
| |____sensors.js
| |____users.js
|____views
| |____error.hjs
| |____index.hjs
In app.js
var express = require('express');
var app = express();
var io = require('socket.io')();
app.io = io;
// notice the `(io)` for the routes that need to be socket-aware
var routes = require('./routes/index');
var users = require('./routes/users');
var sensors = require('./routes/sensors');
var readings = require('./routes/readings')(io);
…
// start listening with socket.io
app.io.on('connection', function(socket){
console.log('a user connected');
});
module.exports = app;
Then in ./routes/readings.js
var express = require('express');
var app = express();
var router = express.Router();
module.exports = function(io) {
router.put('/', jsonParser, function(req, res, next) {
if (!req.body) return res.sendStatus(400);
db.insert(req.body, function (err, newDoc) {
io.emit("reading", {id: newDoc._id});
res.send('Success PUTting data! id: ' + newDoc._id);
});
});
return router;
}
Finally, in the index.hjs template for the client-side
<script src="/socket.io/socket.io.js"></script>
<script>
var socket = io();
socket.on('reading', function (data) {
console.log(data);
});
</script>
The above works. When data are inserted into the db via an http PUT (see readings.js), an event is emitted by io.emit('reading', data) and the browser receives that event and shows it in the console with socket.on('reading', function (data) { … });