This list includes the common system services and their associated ports:
You can also set up system service ports to allow a PC to share its Internet connection with other PCs that are connected to it through the same network. This is known as Internet Connection Sharing (ICS), and it allows the PC that is sharing the connection to provide Internet access for the other networked PCs.
 | If your PC has an application that accepts either web or FTP server connections, the PC sharing the connection might need to open the associated system service port and allow forwarding of incoming connections for those ports. |