How to Enable the Firewall in Lion Server
You use Server Admin to configure a firewall on Lion Server. Using Server Admin to configure a firewall is actually easy. You can click to select services to allow through the firewall, as well as add your own services and ports, such as those used by third-party server software. Server Admin also enables you to create new rules for allowing or blocking ports.
Before you can configure the firewall, you have to enable the firewall service. In Server Admin, the procedure is the same as with other services:
Open Server Admin and select the server in the left column.
Click the Settings icon in the toolbar and then click the Services tab.
Select the Firewall check box and then click the Save button.
As with other services, you also need to start it to get it running:
In Server Admin, click the triangle next to your server in the left column to expand the list of services.
Select Firewall from the list.
Click the Start Firewall button in the lower left.
You can now stop the firewall by clicking the same button, which changes to Stop Firewall. With the firewall stopped, all incoming traffic is allowed.