Callback function socket.io + node.js

Question

There are a client and server side code:

Client:

socket.on('connect',  function() {
        showSystemMessage('Connected.');

        socket.emit('setuser', wm, function(data){
            console.log(data);
            socket.emit('whoisonline', wm, function(data){
                getOnlineFriends(data);
            });
        });
    });

Server:

io.on('connection', function(socket) {
        socket.on('setuser', function (data, cb) {
            cb(data);
        });
});

I get error:

TypeError: undefined is not a function on line 18

Line 18:

socket.on('setuser', function (data, cb) {
     cb(data); // Line 18
});

Then i tried your solution, I got:

TypeError: undefined is not a function in line 35

socket.on('whoisonline', function (data, cb) {
            redis.sinter('user.friend:' + data.id, 'onlineusers', function(error, intersection) {

                friends.online = intersection;
                friends.total  = intersection.length;

                if(friends.total > 0){
                    intersection.forEach(function(entry) {
                        var socketid = clients[entry];
                        io.sockets.connected[socketid].emit('in', { id : data.id, total : friends.total });
                    });
                }

                cb(friends); // Line 35
            });
        });

scopchanov · Accepted Answer · 2018-09-13 09:43:54Z

4

In my case the following works:

at the server side

socket.on('setuser', (name, cb) => { cb(name); });

at the client side

socket.emit('setuser', 'user data', r => { console.log(r); });

edited Sep 13, 2018 at 9:43

scopchanov

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answered Sep 13, 2018 at 9:22

Odeus

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Comments

Lieuwe Rooijakkers · Accepted Answer · 2014-11-06 15:12:50Z

0

Socket.io doesn't work with callbacks, you have to work with .emit() and .on(). In this case your source code would look like:

Client:

socket.on('connect',  function() {
        showSystemMessage('Connected.');

        socket.emit('setuser', wm);
        socket.on("setuser", function(data){
            console.log(data);
            socket.emit('whoisonline', wm);
            socket.on("whoisonline", function(data) { 
                getOnlineFriends(data);
            });
        });
    });

Server:

io.on('connection', function(socket) {
        socket.on('setuser', function (data) {
            socket.emit("setuser", data);
        });
});

answered Nov 6, 2014 at 15:12

Lieuwe Rooijakkers

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4 Comments

AhmedFaud Over a year ago

Hm, thank you, seems work, but I get callback againn after rewrite on your code. Edited question

Lieuwe Rooijakkers Over a year ago

@AhmedFaud Replace line 35 with socket.emit("whoisonline", friends);

JeremyTM Over a year ago

We use socket.io with callbacks all the time. It works fine.

Lieuwe Rooijakkers Over a year ago

@JeremyTM hmm you seem to be right, I must've missed that 5 years ago.

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