Configuring your firewall on Mac OS X 10.6 and later

By default Signal will be added to the application firewall automatically and no configuration is needed. However, if the firewall has been set to “Block all incoming connections” this will block all applications from receiving incoming connections, including Signal.

To configure the firewall:

  1. Open System Preferences, click Security, then click Firewall.
  2. If the firewall is off, no further action is needed.
  3. If the firewall is on, click Advanced.
  4. Ensure that the "Block all incoming connections" option is unchecked, and the "Automatically allow signed software to receive incoming connections" option is checked.

You can read more about the available application firewall options and what they mean at Apple’s support site.