Access to the port 'COM4' is denied

Using Arduino Interfacing w/ Software on the Computer
14

Hmmm, ignore my last post for the moment, I'm running IIS 7 on my PC, and I've just done a very quick and dirty test using a virtual COM port I have installed on my PC, it seems to work first time for me without having to change permissions :frowning:
I did notice though the first time I ran it I forgot to close the serial port at the end of my code, and this actually blocked any further conections, with the same access denied error. Try killing the iis process (I think it's called w3wp.exe) and checking that your code will always close the serial port after each transaction, and this will hopefully work!!!
So you will have something like:

            SerialPort port = new SerialPort("COM8", 9600, Parity.None, 8, StopBits.One);
            try
            {
                port.Open();
                port.WriteLine("Give me data!!!");
                string data = port.ReadLine();
                Response.Write(data);
            }
            finally
            {
                if(port.IsOpen)
                    port.Close();//<---this is the important bit!!!
            }