FTP (20,21): the File Transfer Protocol is deprecated unless it is absolutely necessary. It can be served by
inetd or a standalone daemon.
SSH (22): this is a useful service. Secure Shell is useful for remote command line interface and also file transfer.
SSH is its own daemon, which means it does not rely on inetd.
Telnet (23): this is an older standard for remote shell access. While telnet is useful as a client, a telnet server
is insecure.
HTTP (80): this HyperText Transport Protocol port is useful only if a machine is a web server. It is handled
by Apache or some other HTTP server. As a result, it does not rely on inetd.
IDENT (113): this was used originally for authentication purposes. However, it is now known as the
identification protocol. It is used for a remote server to “call back” a requesting machine.
HTTPS (443): this is secure HTTP. It is similar to HTTP, except the traffic is encrypted. It is useful only on
a web server.
LPD (515): this is Line Printer Daemon, it is only useful if the machine is a print server.
IPP (631): this is Internet Printing Protocol, it is useful only on a print server.