This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for duplex, bidirectional traffic. They usually use port numbers that match the services of the corresponding TCP or UDP implementation, if they exist.

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The Internet Assigned Numbers Authority (IANA) is responsible for maintaining the official assignments of port numbers for specific uses.^[1] However, many unofficial uses of both well-known and registered port numbers occur in practice. Similarly, many of the official assignments refer to protocols that were never or are no longer in common use. This article lists port numbers and their associated protocols that have experienced significant uptake.

The port numbers in the range from 0 to 1023 (0 to 2¹⁰ − 1) are the well-known ports or system ports.^[3] They are used by system processes that provide widely used types of network services. On Unix-like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the well-known ports.^[5]

The range of port numbers from 1024 to 49151 (2¹⁰ to 2¹⁵ + 2¹⁴ − 1) are the registered ports. They are assigned by IANA for specific service upon application by a requesting entity.^[2] On most systems, registered ports can be used without superuser privileges.