You will need to turn your firewall protection to have it running. Here is how to do so.
1. Go to the Apple which is located in the upper left hand corner of the screen.
2. Click on the apple and select "System Preferences" by clicking once on it.
3. The System Preferences window will now open. Under the Internet & Network row, choose Sharing. (See picture) This is the fourth icon over on the row. Select it by clicking on it once.
4. In the Sharing Window click once on the Firewall button.
5. In the Firewall window you must click on Start.
6. By selecting Start you are protecting your computer from being accessed through the Internet.
7. Close this window, you are now finished.
In order to use some of the network services through the firewall, talk to your network administrator or technology support service for that information.