CODEWITHSUNDEEP
javascriptnode.jsexpresssocket.io
Caleb Jay
Caleb Jay

Reputation: 2199

Should I put server-side listeners on io or socket for socket.io?

If I have my express.js server set up as such: 

var express = require('express');
var app = express();
var server = require('http').Server(app);
var io = require('socket.io')(server);
var port = process.env.PORT || 8080;

server.listen(8080);

And elsewhere I have a io.on('connnect', function(socket){...}); , should I be putting emit/event listeners on that socket within the io.connect(...) callback, or on the io object?

My basic program flow is as follows:

  1. Client socket emits get_new_number.
  2. Server receives get_new_number from unique socket.
  3. Based on that unique socket ID, it emits new_number
  4. The client listens for new_number and logs the data within to the console when triggered.

On the server-side, for part 2, I believe that must be a within the io.on('connect'...) function, so I can access socket.id for use later :

io.on('connect', function(socket){
    socket.on('get_new_number', function(){
        console.log('server got request for new number.');
        globalVarId = socket.id;        
    });
});

But from there, where should I emit a new number to that unique socket? Say I save the socket.id and then emit to only it, how can I do that? The below isn't working: 

io.on('connect', function(socket){
    //get_new_number stuff
    socket.to(globalVarId).emit('new_number', {number: someNumber});
});

Should I instead later do a io.to(globalVarId).emit... ?

EDIT: For that matter, is there a way to put event listeners on the io object, such like 

io.on('someEvent', function(socket){
    console.log('this socket did a thing, ', socket.id);
});

Upvotes: 0

Views: 122

Answers (1)

robertklep
robertklep

Reputation: 203231

You can assume that socket within the callback function represents a unique client/connection.

So when you want to communicate with that client, you can use socket.emit():

io.on('connect', function(socket) {
  socket.on('get_new_number', function() {
    console.log('server got request for new number.');
    //get_new_number stuff
    socket.emit('new_number', { number: someNumber });
  });
});

.to(...).emit(...) is used for something else entirely (sending a message to a particular room).

Upvotes: 1

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