Success Callback for emit method in socket.io

Question

Im trying to emit a custom message from my client. I need to perform some actions on its success and failure. Now, how can i attach the success callback to emit method?

Answer 1

The reason why your second code is not doing anything is because exposed events in socketIO are just defined for socket.on methods. Therefore you need to add another emit in your server app.js to accomplish this

Client emits the custom message and sends JSON data to the socket via socket.emit, also he gets an update function that handles the success callback

socket.emit ('message', {hello: 'world'});
socket.on ('messageSuccess', function (data) {
 //do stuff here
});

Server-side Gets a call from the message emit from the client and emits the messageSuccess back to the client

socket.on ('message', function (data) {
 io.sockets.emit ('messageSuccess', data);
});

You could probably make a module out of this behavior so you can attach this for every message that you want to be handled that way.

Answer 2

If you look at the docs, it shows you an example of passing a call back function -2nd last example: http://socket.io/docs/#Sending-and-getting-data-acknowledgements

Ex server:

    socket.on('formData', 
              function(data, fn){
                      // data is your form data from the client side
                      // we are here so we got it successfully so call client callback
                      // incidentally(not needed in this case) send back data value true 
                      fn(true);
              }
             );

client:

      socket.emit('formData', 
                  data, 
                  function(confirmation){
                          // send data
                          // know we got it once the server calls this callback      
                          // note -in this ex we dont need to send back any data 
                          // - could just have called fn() at server side
                          console.log(confirmation);
                  }
                 );