"Dimmer" noob question

Using Arduino Interfacing w/ Software on the Computer
15

Arduino code:

const int ledPin = 9;      // the pin that the LED is attached to

void setup()
{
  // initialize the serial communication:
  Serial.begin(9600);
  // initialize the ledPin as an output:
  pinMode(ledPin, OUTPUT);
}

void loop()
{
  byte brightness;

  // check if data has been sent from the computer:
  if (Serial.available())
  {
    // read the most recent byte (which will be from 0 to 255):
    brightness = Serial.read();
    Serial.print("brightness: [");
    Serial.print(brightness);
    Serial.println("]");    // set the brightness of the LED:
    analogWrite(ledPin, brightness);
  }
}

Processing code:

import processing.serial.*;
Serial port;

void setup()
{
  size(256, 150);

  println("Available serial ports:");
  println(Serial.list());

  // Uses the first port in this list (number 0).  Change this to
  // select the port corresponding to your Arduino board.  The last
  // parameter (e.g. 9600) is the speed of the communication.  It
  // has to correspond to the value passed to Serial.begin() in your
  // Arduino sketch.
  port = new Serial(this, Serial.list()[1], 9600);  

  // If you know the name of the port used by the Arduino board, you
  // can specify it directly like this.
  //port = new Serial(this, "COM1", 9600);
}

void draw()
{
  // draw a gradient from black to white
  for (int i = 0; i < 256; i++)
  {
    stroke(i);
    line(i, 0, i, 150);
  }

  // write the current X-position of the mouse to the serial port as
  // a single byte
  port.write(mouseX);
}

void serialEvent(Serial port)
{
  char c = (char)port.read();
  print(c);
}

Processing output:

Available serial ports:
WARNING:  RXTX Version mismatch
	Jar version = RXTX-2.2pre1
	native lib Version = RXTX-2.2pre2
[0] "COM3"
[1] "COM13"
brightness: [0]
brightness: [0]
brightness: [0]
brightness: [0]
brightness: [0]
brightness: [1]
brightness: [3]
brightness: [5]
brightness: [6]
brightness: [8]
brightness: [10]
brightness: [10]
brightness: [11]
brightness: [12]
brightness: [13]
brightness: [13]
brightness: [13]
brightness: [13]
brightness: [13]
brightness: [13]
brightness: [13]
brightness: [13]