Information about TCP/IP port assignments

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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: 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.