Possible spawn stdin problem

gistfile1.js

var spawn = require('child_process').spawn,
    cs    = spawn('/Users/mattpardee/Work/test/node_modules/coffee-script/bin/coffee', []);

cs.stdout.on('data', function (data) {
  console.log('stdout: ' + data);
  setInterval(function() {
      console.log(cs.stdin.bytesWritten, cs.stdout.bytesRead);
      cs.stdin.write('number = 42\n');
  }, 1000);
});

cs.stderr.on('data', function (data) {
  console.log('stderr: ' + data);
});

cs.on('exit', function (code) {
  console.log('child process exited with code ' + code);
});