Information about TCP/IP port assignments

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This article was previously published under Q174904
This article has been archived. It is offered "as is" and will no longer be updated.
This article provides information about port assignments for various TCP/IPports. This was previously documented in RFC 1700.

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



The port numbers are divided into three ranges: the Well Known Ports, theRegistered 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.


The Well Known Ports are assigned by the IANA and on most systems can onlybe used by system (or root) processes or by programs executed byprivileged users. Ports are used in the TCP [RFC793] to name the ends oflogical connections which carry long term conversations. For the purposeof providing services to unknown callers, a service contact port isdefined.

The contact port is sometimes called the "well-known port" .To the extentpossible, these same port assignments are used with the UDP [RFC768]. Theassigned ports use a small portion of the possible port numbers. For manyyears the assigned ports were in the range 0-255. Recently, the range forassigned ports managed by the IANA has been expanded to the range 0-1023.


The Registered Ports are listed by the IANA and on most systems can beused by ordinary user processes or programs executed by ordinary users.Ports are used in the TCP [RFC793] to name the ends of logical connectionswhich carry long term conversations. For the purpose of providing servicesto 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 onthe Information Sciences Institute Web site at the following location:Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

Article ID: 174904 - Last Review: 12/05/2015 08:06:52 - Revision: 3.4

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