Information about TCP/IP port assignments (174904)


The information in this article applies to:

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  • Microsoft Windows 98
  • Microsoft Windows 95
  • Microsoft LAN Manager 2.2c
  • Microsoft Network Client for MS-DOS 3.0
This article was previously published under Q174904

SUMMARY

This article provides information about port assignments for various TCP/IP ports. This was previously documented in RFC 1700.

The assignments are now listed as living documents, regularly updated and revised when new information is available and new assignments are made. The specific location of the port numbers list is now available at the following Web site:

http://www.iana.org/assignments/port-numbers


MORE INFORMATION

PORT NUMBERS

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.
  • The Registered Ports are those from 1024 through 49151.
  • The Dynamic and/or Private Ports are those from 49152 through 65535.

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.

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 assigned ports use a small portion of the possible port numbers. For many years the assigned ports were in the range 0-255. Recently, the range for assigned ports managed by the IANA has been expanded to the range 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.

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.

For information about specific TCP/IP port assignments, see RFC 1700 on the Information Sciences Institute Web site at the following location:

ftp://ftp.isi.edu/in-notes/rfc1700.txt

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Modification Type:MinorLast Reviewed:12/16/2004
Keywords:kburl kbinfo KB174904 kbAudDeveloper
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