According to IANA....
WELL KNOWN PORT NUMBERS
The Well Known Ports are assigned by the IANA and on most systems can
only be used by system (or root) processes or by programs executed by
privileged users.
Ports are used in the TCP [RFC793] to name the ends of logical
connections which carry long term conversations. For the purpose of
providing services to unknown callers, a service contact port is
defined. This list specifies the port used by the server process as
its contact port. The contact port is sometimes called the
"well-known port".
To the extent possible, these same port assignments are used with the
UDP [RFC768].
The range for assigned ports managed by the IANA is 0-1023.
REGISTERED PORT NUMBERS
The Registered Ports are listed by the IANA and on most systems can be
used by ordinary user processes or programs executed by ordinary
users.
Ports are used in the TCP [RFC793] to name the ends of logical
connections which carry long term conversations. For the purpose of
providing services to unknown callers, a service contact port is
defined. This list specifies the port used by the server process as
its contact port.
The IANA registers uses of these ports as a convenience to the
community.
To the extent possible, these same port assignments are used with the
UDP [RFC768].
The Registered Ports are in the range 1024-49151.
DYNAMIC AND/OR PRIVATE PORTS
The Dynamic and/or Private Ports are those from 49152 through 65535.
