mock pop3 server です。常にOKと返すだけ、メールボックスは空

mock-pop3-server.js

var net = require('net');
var readline = require('readline');

net.createServer(function (socket) {
    socket.write("+OK Mock-Pop3-Server Ready."+"\r\n") ;

    readline.createInterface(socket, socket).on('line', function (line) {
        var msg = "-ERR unknown command"+"\r\n";

        var slicedLine = line.slice(0, 4).toUpperCase();
        switch (slicedLine) {
            case 'USER':
                msg = '+OK'+"\r\n";
                break;
            case 'PASS':
                msg = '+OK'+"\r\n";
                break;
            case 'STAT':
                msg = '+OK 0 0'+"\r\n";
                break;
            case 'LIST':
                msg = '+OK 0 messages'+"\r\n";
                break;
            case 'QUIT':
                msg = '+OK dewey POP3 server signing off (maildrop empty)'+"\r\n";
                break;
        }

        socket.write(msg);
    });

}).listen(110);