[ PORT DIRECTORY ]

Every port we've researched.

Each port below has a researched page — what IANA assigned it to, what really listens there, how it is commonly abused, and which ports you would expect to see alongside it. They're grouped by the IANA ranges, because where a port sits in the number space tells you something before you read anything else: whether it was assigned at all, and whether a process needed privileges to bind it. Ports we haven't researched aren't listed — they don't have a page yet, though you can still look any number up with the Port Lookup.

TCP and UDP each have their own 16-bit port space, so the same number can be two unrelated services depending on transport. Where we have researched both, one page covers them together and the row below says which transports it carries.

Well-known ports 485 ports

Assigned by IANA and, on Unix-like systems, historically bindable only by a privileged process. Range 0–1023.

Registered ports 56 ports

Assigned by IANA on request. Any process may bind them. Range 1024–49151.

Dynamic and private ports 1 port

Never assigned. Used for ephemeral client-side sockets and private services. Range 49152–65535.

What a port number actually is.

A port is not a place. It is a 16-bit number in a TCP or UDP header that tells the receiving host which listening process a packet belongs to. One machine on one IP address can run a web server, a mail server and a database at the same time because each one has claimed a different number, and the kernel uses that number to hand each arriving packet to the right process.

IANA maintains the registry that says which service a number is meant to carry, and splits the space into three ranges. The well-known range, 0 to 1023, holds the assignments most people can name — 22, 25, 53, 80, 443 — and on Unix-like systems a process historically had to be privileged to bind one. The registered range, 1024 to 49151, is assigned on request and is where most application-specific services live. The dynamic range above 49151 is never assigned: it is where your own machine picks a temporary source port every time it opens a connection.

The registry records intent, not reality. Nothing stops a process binding a number assigned to something else, and plenty do — which is exactly why an unexpected listening port is worth looking up rather than assuming.

What each page contains

Every entry linked above has a page written from primary sources: the IANA Service Name and Transport Protocol Port Number Registry, the RFC or specification the assignment cites, and public documentation for the software that actually uses it. A page sets out the assigned service name, what typically listens there in practice, the security implications worth knowing, and related ports you would expect to see nearby. Where a fact could not be verified, the page says so rather than guessing.

511 of the 542 ports listed here carry an IANA service name. The rest are researched pages for numbers IANA leaves unassigned or reserved, which are often the more interesting ones — an unassigned port with real traffic on it usually means something specific.