Several questions concerning serial communication

Hi,

I am currently programming a Matlab Script(with GUI via guide) to make use of a measurement system from the 90s that is connected via RS-232 to the computer.

I have several questions concerning the serial communication:

1. Is there a way to close the serial connection I opened in the script via workspace? When I am debugging my code and there is an error before the connection is closed I now need to restart Matlab. "fclose('all')" sadly doesn't work.

2. After I hit start on the Gui I want to read from the serial port as long as there is an inflow or I press the stop Button. I tried a global variables that turns on after the "Stop" button is pressed.

while isstopped == 0  && its.BytesAvailable > 0
  income = fgetl(its)
  .
  .
  .

But even though I set the ReadAsyncMode of the connection to continouus the income stops after approximately 30 lines. The Stopbutton doesn't work either.

I am grateful for any answers.

Best Regards,

Florian