If your firewall is set up to allow LW & port is open then you should be able to use DC.
Did you configure your firewall so it allows LW full access (advisable not to have 2 active firewalls b/c they can interfere with each other);
Firewall configuration instructions (click on link)
Just to check: Do this test:
Bug Report instructions & sample image Is the result True/False? If False then your firewall is probably still partially blocking.
They need to be the same; have their firewall properly configured to allow LW full access.
If you know these friends well, you can also send them a magnet link. After they start downlding it then they can browse you & vice-versa for you from the monitor window. But you'd both need to have chat enabled also. (See Open Discussion section stickys about this.)