Any data exchange for any network service to or from a computer uses interface channels of input and output in its communications protocol. These interface channels of access are called network ports. For a comprehensive list of most ports used, see the IANA web site http://www.iana.org/assignments/port-numbers or see Security Portal’s page at http://www.securityportal.com/firewalls/ports/ for greater detail.
A network protocol generally consists of a port number(s) and a transport type. The transport types in the case of most Stanford University services are either TCP or UDP.