Remote access port numbers: ssh, telnet, 3389 and 5900

By Liam CooperOctober 27, 2026IANA registry as updated October 26, 2026

IANA assigns port 22 to ssh, 23 to telnet, 3389 to ms-wbt-server, labelled “MS WBT Server”, and 5900 to rfb, labelled “Remote Framebuffer”. The X Window System holds a whole block: x11 is assigned on TCP and UDP for every number from 6000 to 6063.

Those five entries look alike on a port list, but the registry records them very differently. Some cite a specification, some carry a date, and one is a range rather than a number. The tables below put them side by side, together with the older Berkeley remote commands that still hold numbers in the System Port range.

The remote-session entries

Only three of these cite an RFC. ssh cites RFC 4251, “The Secure Shell (SSH) Protocol Architecture” (January 2006), and is one of the 88 numbers that also carry an SCTP entry. telnet cites RFC 854, the 1983 Telnet specification, which is still an Internet Standard. rfb cites RFC 6143, an Informational RFC from 2011, five years after IANA recorded the assignment in March 2006.

The entry for 3389 has no registration date and no reference; the registry last modified it on November 3, 2022. A second Microsoft entry, vmrdp on 2179 (“Microsoft RDP for virtual machines”), dates from March 2007. Numbers such as 5800 and 5938 carry no assignment at all, so they appear in the registry only as part of a free run.

The Berkeley r-commands

Ports 512, 513 and 514 show how the early registry split one number between two services. On 512, TCP belongs to exec and UDP to biff (also listed as comsat). On 513, TCP is login and UDP is who. On 514, TCP is shell and UDP is syslog; the syslog side cites RFC 5426 and has its TLS form on port 6514. The labels on these entries are written as full sentences rather than names.

Names built on ssh and telnet

Elsewhere in the registry, 5 other names carry “ssh” as a separate part of the name and 4 carry “telnet”. Examples are netconf-ssh on 830 and telnets on 992, which the registry labels “telnet protocol over TLS/SSL”.

The X11 block

The x11 assignment is one of eight port ranges in the registry. It covers 64 numbers, 6000 to 6063, on TCP and UDP, with the label “X Window System”. Because the range holds the whole block, none of those 64 numbers has an entry of its own; the ports 6000–6999 page shows the range as one row, followed by the next assigned number above it.

How many labels mention remote access

A search of the registry labels for the word “remote” returns 130 service names on 124 numbers. 29 of them are assigned on TCP alone and 74 carry a registration date. The match is broad: it includes remote procedure calls, remote monitoring and remote file systems as well as remote sessions. The lookup runs the same search and lists every match with its protocols.

The word appears in many kinds of label. Counting the word that follows “remote”, the most common are “control” (11), “management” (10) and “access” (6). Most of the matches, 107, sit in the User Ports; 23 are System Ports. Of the dated ones, 54 were registered before 2011 and 20 from 2011 on, the latest being minirem on 4120, registered on September 28, 2017.

How the ssh and telnet references have aged

The RFC Editor index records later changes to the documents these entries cite. RFC 4251 has been updated by RFC 8308 and RFC 9141 but not obsoleted, so the registry reference is still the current architecture document. RFC 854 for telnet has one update, RFC 5198, and keeps its Internet Standard status after more than four decades. RFC 6143 for rfb has no later changes recorded.

Management entries

wsman on 5985 and wsmans on 5986 form a plain and TLS pair, labelled “WBEM WS-Management HTTP” and the same “over TLS/SSL”, both registered in November 2006. xdmcp on 177, the X Display Manager Control Protocol, has no TLS form and no date.

For the full context of any of these numbers, the range pages list every neighbor: ports 0–99 for ssh and telnet, ports 3000–3999 for 3389 and ports 5000–5999 for rfb.