How to call acknowledgment functions in SocketIO?

Question

Following the documentation on the SocketIO website, I have the following code:

Server

socket.on('foo', (arg, ack) => {
    //Do stuff with arg
    if(ack)
        ack('response');
});

Client

socket.emit('foo', arg, (response) => {
    console.log(response);
});

However, the ack function is never called. As a matter of fact, it is undefined. I am using SocketIO v2.0.4 on both server and client side.

Am I missing something? The docs make it look like it should be that easy, yet I just can't figure it out!

Thanks!

Answer 1

Server side

var io = require('socket.io')(8090);

io.on('connection', function (socket) {
  console.log('connected')
  socket.on('ferret', function (arg, ack) {
    console.log('ferret')
    ack('woot');
  });
});

Client side

const ioClient = require('socket.io-client');
var client = ioClient.connect('http://localhost:8090');
client.emit('ferret', 'tobu', (response) => {
  console.log(response)
  console.log('ack')
});

It will log the response of ack() and the 'ack' string. I got the reference socket.io acknowledge node.js sample.

Answer 2

Server

socket.on('foo', (arg) => {
//Do stuff with arg
    console.log('message from client : ' + data)
    socket.emit('bar','message acknowledge from server');
});

Client

socket.emit('foo', 'mymessage');
socket.on('bar', (data) => {
    console.log(data)
});

using socket.io in server side and socket.io-client in client side

Server side

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

app.listen(80);

io.on('connection', function (socket) {
    socket.emit('news', { hello: 'world' }, function(res) {
        console.log(res);
    });
});

Client side

var io = require('socket.io-client');

var socket = io('http://localhost');
socket.on('news', function (data, ack) {
    console.log(data);
    if(ack){
        ack("acknowledge from client");
    }
});