basic smtp server in node.js

I'm trying to write a dumb (braindead) smtp server in node.js to act as a stub server for testing other applications.

I have a basic set of responses, and it works great with telnet.

However, when my php/Codeigniter app uses it, it runs so slowly as to be useless, and I get occasional fwirite() broken socket errors.

• The php app runs fine using a real smtp server
• The node.js app runs fine when using telnet

Am I missing a critical or obvious step? Is there something about sockets or system pointer resources that I'm mishandling?

It's pretty quick & dirty but that was the point:

var net = require('net');

net.createServer(function (socket) {

  var mode = 'nodata';

  socket.on('data', function(data) {

    var data_string = data.toString();
    console.log(data_string);

    if (mode == 'nodata') {

      if (data_string.substring(0, 4) == 'EHLO') {
        socket.write('hello ' + data_string.substring(5, data_string.length - 1) + '\r\n');
      } else if (data_string.substring(0, 10) == 'AUTH LOGIN') {
        socket.write('250 ok\r\n');
      } else if (data_string.substring(0, 10) == 'MAIL FROM:') {
        socket.write('250 ok\r\n');
      } else if (data_string.substring(0, 8) == 'RCPT TO:') {
        to = data_string.substring(8, data_string.length - 1);
        socket.write('250 ok its for ' + to + '\r\n');
      } else if (data_string.substring(0, 4) == 'DATA') {
        socket.write('354 ok send it\r\n');
        mode = 'data';
      } else if (data_string.substring(0, 4) == 'QUIT') {
        socket.write('221 Goodbye\r\n');
        socket.end();
        return;
      }

    } else if (mode == 'data') {

      if (data_string.substring(0, 1) == '.') {
        socket.write('250 message queued\r\n');
        mode = 'nodata';
      }

    }

  });

}).listen(3434);