linux
http://www.iana.org/assignments/port-numbers
PORT NUMBERS (last updated 2011-06-28) The port numbers are divided into three ranges: the Well Known Ports, the Registered Ports, and the Dynamic and/or Private Ports. The Well Known Ports are those from 0 through 1023. DCCP Well Known ports SHOULD NOT be used without IANA registration. The registration procedure is defined in [RFC4340], Section 19.9.