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
Some services are predefined for ICF and ICS. FTP Server, Internet Mail Server, Secure Web Server, Telnet Server, and Web Server are examples of built-in services. These services can run on the ICS client computers or on your ICF or ICS host computer. You can add a new service to your network by installing the service software on one of your network computers and then adding the service definition so that ICS and ICF, if one or both are enabled, will allow the service to be accessed from the Internet. Services that are preconfigured require that only the name or IP address of the computer hosting the service for the service definition. For built-in services, information such as the description of the service and TCP or UDP port number of the service are built in and cannot be changed. For more information, see Edit a service definition