Service definitions overview
Services run transparently to support other programs. An example of a service is an HTTP Web server that supports hosting Web pages from your home or small office network. If you have an HTTP Web server service enabled for your network, you can use that service to supply your own Web pages to the Internet. In addition to having a Web server on your network, you can have an FTP service that permits users to upload or download files through the Internet, an Internet mail server for storing and forwarding e-mail, and a variety of other services.

In order to permit the traffic to flow from the Internet to the computer hosting the service, you must add the service to the Services list by entering information about the services' operational settings on the Services tab of the Internet Connection Sharing (ICS) or Internet Connection Firewall (ICF) host computer. The set of operational settings provides the parameters that are required in order for ICF to allow traffic to travel from the Internet to the network and ICS to forward traffic. The operational settings are known as a "service definition," because they define that required environment. The information that you must enter to add a service definition includes: the description of the service, the name or IP address of the computer hosting the service, and the TCP or UDP port number of the service. For more information, see Add a service definition.

To add a service definition
Open Network Connections.
Click the shared connection or the Internet connection that is protected by Internet Connection Firewall, and then, under Tasks, click Change settings of this connection.
On the Advanced tab, click Settings.
On the Services tab, click Add and enter all of the following information:
In Description of service, type an easily recognized name for the service.
In Name or IP address of the computer hosting this service on your network, type the name or IP address of the computer that runs the service.
In External port number for this service, type the port number that external computers will use to contact this service.
In Internal Port number for this service, type the port number that the service on your network is using.
Click either TCP or UDP.

You can obtain the correct configuration values for the TCP or UDP port number from the service's documentation or Web site.