Getting a node.js process to stop accepting input upon "quit" command from user

I wrote a basic TCP client as specified in Professional Node.js.

//TCP Client
var net = require('net'); 
var port = 4000;
var conn;

process.stdin.resume();

(function connect() {
  conn = net.createConnection(port);

  conn.pipe(process.stdout, {end: false});
  process.stdin.pipe(conn); 

  process.stdin.on('data', function(data) {
    if (data.toString().trim().toLowerCase() === 'quit') {
      conn.end();
      process.stdin.pause(); 
    }
  });
}());

When the user enters 'quit', I want the process to end its connection to the TCP server and stop accepting input from STDIN.

When I do this now, I get the following error:

> quit
ReferenceError: quit is not defined

And after this, the code in my if statement is not run.

How do I fix this?