What prevents the opening of TCP\UDP ports?

Question

Computer networks

The laptop (Windows 7 OS) has two user accounts. One local, the second domain. From under the domain user at a local network connection certain TCP\UDP ports are not opened. From under the local user of problems is not present.
How to determine what prevents the opening of ports?

Answer 1

Check
netstat -na | find "27500"
perhaps you already have a port open from another user?

Answer 2

firewall?
And what is meant by certain ports? What service should open them?