I am trying to talk to my Arduino (Due and UNO) boards from a winforms app.  I have a simple form that passes a 1 or 2 for turning an LED on and off.

However,  my Winforms app complains that the port is already being used.   

What I am trying to accomplish is to see if the correct value is being passed (read) from my Winforms app.   

Here is the example video I am trying to follow: http://www.youtube.com/watch?v=c-3mo3LRgUg

I have my LED in 13 and ground.  Here is the Arduino Code in the loop:

[code]if(Serial.available())
     { 
           int _iInp = Serial.read(); 
           switch(_iInp) 
           { 
           case '1': 
                 { 
                       //Serial.println("HIGH");
                         digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
                         //analogWrite(led, HIGH);
                 } 
           case '2': 
                 { 
                       //Serial.println("LOW");
                        digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
                        //analogWrite(led, LOW);
                 } [/code]

Any ideas?