arduino+processing=proplem

Projects Interfacing w/ Software on the Computer
8 
  Serial.println('0');
  Serial.println("1");

I like consistency. Too bad there isn't any here.

if(sensorValue>600){
  analogWrite(ledpin,0);
  Serial.println('0');
}
if((sensorValue<490)&&(sensorValue>350)){
  analogWrite(ledpin,50);
  Serial.println("1");
}
if(sensorValue<350)
{analogWrite(ledpin,255);
Serial.println('1');
}

So, if sensorValue is between 350 and 490 (that if statement is backwards) send a 1. If it is less than 350, send a 1. If it is greater than 600, send a 0. If it is between 490 and 600, forget it. Do nothing.

What you are setting the LED pin to and what you are sending to the serial port are not consistent.

void serialEvent (Serial port)
{index=port.read();
  if(index=='1')
{
    
  bool="dark";
brightness=0;
}
if(index=='0')
{
  bool="light";
  brightness=255;
}}

What if index is 10 or 13? You are sending those values, too.