How To Send Data From The Arduino To MATLAB

I am trying to establish this connection using the same code in the link
How To Send Data From The Arduino To MATLAB

but when I run the Matlab I get this error

Error using serial/fopen (line 72)
Open failed: Port: COM4 is not available. No ports are available.
Use INSTRFIND to determine if other instrument objects are connected to the requested device.

Please any body has an idea why I am getting this error???

sorry
this is the link

Isn't it obvious that you are using the wrong serial port in MATLAB?

Use the same port that you use to program the Arduino.

Have you tried using the Support package to send information from Arduino to MATLAB? Arduino Support from MATLAB - Hardware Support - MATLAB & Simulink