ICQ and AIM support a number of options beyond simple instant messaging. These options include direct chat and file transfers. For those to function, the instant messaging system must allow new connections initiated from remote systems. This option will open a specified port range on the firewalled system. The client on the firewalled system must also be configured to use the specified port range. This option allows inbound ports to a client running on the firewalled computer. It does not enable port forwarding to a computer on an internal network behind the firewall.