node.js socket.io middleware

Question

In node.js we can add some middleware function to socket.io server like this

 io.use(function(socket, next) {
            var req = socket.handshake;
            var res = {};
            cookieParser(req, res, function(err) {
                if (err) return next(err);
                session(req, res, next);
            });
        });

I wonder if we can add some kind of middleware to simple socket.on function as in the following example

io.sockets.on('connection', function(socket){
    socket.on('someSignal',
             function(data,next){/*middleware function code*/ next();},
             function(data){})
});

Answer 1

emitter.on(event, listener) is the alias for emitter.addListener(event, listener). if you want to do this, every request pass through this middleware will add one eventListener.