Can I separate socket.io event listeners into different modules?

I usually split various client related functionality (I usually call them handlers) into individual modules, and then require and use them in whatever file creates the socket.io connection.

Here is an example module, that exports a function which expects to be passed a socket.io client:

/* register-handler.js */
module.exports = function (client) {
  // registration related behaviour goes here...
  client.on('register', function (data) {
    // do stuff
  });
};

Which is consumed by a file that creates a new socket, listens for connections, and passes them to the handler, which then listens to events on the client.

/*  main.js */
// require your handlers
var handleRegister = require('./register-handler');

// .. set up socket.io

socket.on('connection', function (client) {
  // register handlers
  handleRegister(client);
});

Here is one way

socket.on("connection", function (client) {

    console.log("Client connected to socket!");

    require('./login')(socket, client);
    require('./register')(socket, client);
});

login.js

module.exports = function(socket, client) {
    client.on("login", function (data) {

        validate(data){

            socket.sockets.emit("login_success", data);

        }

    });
};