socket.io: client-side emit callback never fires

Question

Messing around with socket.io just for proof of concept, everthing is working great so far except I can\'t get my emit callback to work on the client side. I\'ve got to be m

Answer 1

In Liam William's answer, I found it was necessary to send the callback (or acknowledgement function) as the third argument on the client emit:

Client:

<script src="http://localhost/socket.io/socket.io.js"></script>
<script>
var socket = io.connect('http://localhost');
socket.emit("getSomeData", null, function(data) {
    console.log(data);
});

Answer 2

It looks like you have some logic switched around, try...

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
    socket.emit("getSomeData",{data: "some random data"});
});

and client...

<script src="http://localhost/socket.io/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost');
  socket.on("getSomeData", function(data) {
      console.log(data);
  });
</script>

EDIT:

var io = require('socket.io').listen(80);

io.sockets.on('connection', function (socket) {
    socket.on("getSomeData", function(name,fn) {
        fn({data: "some random data"});
    });
});

Client

<script src="http://localhost/socket.io/socket.io.js"></script>
<script>
  var socket = io.connect('http://localhost');
  socket.emit("getSomeData", function(data) {
      console.log(data);
  });
</script>

Answer 3

You can have the callback, but you have to do it a bit differently:

---

Server: (app.js)

var io = require('socket.io')(80);

io.on('connection', function (socket) {
// please note that server will take 2 data entries as function parameter below
  socket.on('ferret', function (name, fn) {
    fn('woot');
  });
});

---

Client (index.html)

var socket = io(); // TIP: io() with no args does auto-discovery
socket.on('connect', function () {
socket.emit('ferret', 'tobi', function (data) {
    console.log(data); // data will be 'woot'
});
});

Actaully, socket io also mentions this one; sending-and-getting-data-(acknowledgements)