(FTP) WSAEACCES An attempt was made to access a socket in a way forbidden by its access permissions

Question
(solution is below)

Today one of my customer’s got the following connect error when running my application. This same application works just fine on my system as well as almost 100 others. It had run correctly on her computer until she installed an upgrade.

The connect error is:
Port: 21
Host: www.***.com
sockError: 10013
Connect: failed
WSAEACCES An attempt was made to access a socket in a way forbidden by its access permissions
Reason: 7

Do you have any ideas on what I should have her change on her system to get this to work? Her firewall was off. I turned it on and added my program as an exception. I got the same error.
I added port 21 as a TCP port but that didn’t change the result either.

Solution:

I got an answer from the customer’s computer tech.
The computer had MacAfee anti-virus installed and it was blocking port 21.
He uninstalled the virus scan and the FTP started to work again.