1. Open System Preferences and go to Security section

2. In Security section go to Firewall tab.
3 In the list of exceptions find Amule.app entry.
3 If Amule.app is listed, select it and press "-" button below the list. After go to step 4.
If there is no Amule.app in the list skip to step 4.

4. Press the "+" button below the list. File chooser will open.

5. In the Applications folder select Amule.app and click "Add" button.

6. Check that Allow incoming connections is set for Amule.app

Close System Preferances>