Skip to main content

6. Port Number Ranges

6. Port Number Ranges​

TCP, UDP, UDP-Lite, SCTP, and DCCP use 16-bit namespaces for their port number registries. The port registries for all of these transport protocols are subdivided into three ranges of numbers:

  • the System Ports, also known as the Well Known Ports, from 0-1023 (assigned by IANA)
  • the User Ports, also known as the Registered Ports, from 1024-49151 (assigned by IANA)
  • the Dynamic Ports, also known as the Private or Ephemeral Ports, from 49152-65535 (never assigned)

Of the assignable port ranges (System Ports and User Ports), individual port numbers are in one of three states at any given time:

  • Assigned: Assigned port numbers are currently assigned to the service indicated in the registry.
  • Unassigned: Unassigned port numbers are currently available for assignment upon request.
  • Reserved: Reserved port numbers are not available for regular assignment; they are "assigned to IANA" for special purposes.

6.1. Service Names and Port Numbers for Experimentation​

Port numbers in the Dynamic Ports range are not assigned by IANA and MUST NOT be registered. However, when documents describing new applications or services need to provide examples, port numbers need to be provided. To reduce the likelihood of operational problems caused by unregistered use of IANA-assigned port numbers, this document makes the following port number ranges available for experimentation purposes:

  • the System Ports range: ports 1021-1023 (3 values)
  • the User Ports range: ports 49128-49150 (23 values)

These ranges are designated for testing purposes, and can be used to experiment with new protocols and services.

Last updated on