socket.send outside of io.sockets.on( )

Question

I have a loop that querys a database continuously. When the query returns a result, the node.js app will send a message to every client connected to the node server via socket.io v0.8.

Problem: io.sockets.broadcast.send('msg') is called in the middle of a setInterval() loop so it is not within an io.sockets.on()'s callback function and thus this will not work. When io.sockets.send('msg') is used, no message seems to be sent to the client.

Node.js code

setInterval(function() {
    util.log('Checking for new jobs...');
    dbCheckQueue(function(results) {
        if (results.length) {
            io.sockets.broadcast.send('hello');
        }
    });
}, 10*1000);

However, if the setInterval is to be called from within io.sockets.on('connection',..), every connected client will create an additional loop!

Node.js code

io.sockets.on('connection', function(socket) {
    setInterval(function() {
        util.log('Checking for new jobs...');
        dbCheckQueue(function(results) {
            if (results.length) {
                io.sockets.send('hello');
            }
        });
    }, 10*1000);
});

Clientside JS

        socket.on('hello', function() {
            console.log('HELLO received');
        })

*How can I get a SINGLE loop to run, but still be able to send a message to all connected clients?

Solution 1

I think that this will successfully solve your problem

io.sockets.emit('hello')

Solution 2

Improving previous answer from @Nyxynyx

io.sockets.emit('hello')

It is equivalent to:

io.of('/').emit('hello');

If you need a different route, change the of function parameter.

Documentation: https://socket.io/docs/v3/server-api/index.html#server-sockets

Comments

[Eliasdx]

io.sockets can be accessed outside of io.sockets.on.

[Nyxynyx]

@Eliasdx When I use io.sockets.broadcast.send('hello') outside, I get the error TypeError: Cannot call method 'send' of undefined

[Eliasdx]

you can only use broadcast on a socket, e.g. socket.broadcast.send within a io.sockets.on-callback. however i think you can send to all clients with io.sockets.send (with io. and without broadcast).

[Nyxynyx]

It appears that none of the clients can receive it if I use io.sockets.send('hello')

[Eliasdx]

Hum. if you want to use socket.on('hello',...) you must use socket.emit instead of socket.send.

[Nyxynyx]

If I want to send a message to all clients outside of the io.sockets.on callback function, is io.sockets.send() the only function I can use? If so, what should I use on the client side instead of socket.on('hello', ...)

[Eliasdx]

Just use io.sockets.emit('hello') to send the msg. socket.io/#how-to-use

[Nyxynyx]

@Eliasdx Awesome, that works.

[Deepak M]

Could you tell me how & where to put the io.sockets.emit('some_link') in my question - https://stackoverflow.com/questions/45435498/how-to-use-sock‌​et-ioemit-function-o‌​utside-of-socket-fun‌​ction-nodejs-express ?

[Hossein]

Thanks! you saved my day.

[Kyle Corbin Hurst]

For anyone in the future: io.of('/').emit('hello'); is actually the better function to use if you're using the redis adapter and rooms: io.of('/').adapter.remoteJoin(user.socket_id, data.conversation.id);. The reason being is that io.sockets will emit for every person that joins a room.