Port Number Lookup

When a firewall log, a scan result or a configuration file mentions port 5432 or 3389, the number alone says little. The page searches the official IANA registry of assigned ports and tells you the standard use, the protocols and the range. It works from a copy of the registry stored on this site.

The three ranges

Port numbers are 16-bit values, so they go from 0 to 65535. Ports 0 to 1023 are the well-known or system ports, assigned for core services such as 22 for SSH, 53 for DNS, 80 for HTTP and 443 for HTTPS; on Unix-like systems only privileged processes can open them. Ports 1024 to 49151 are registered ports, which organisations ask IANA to assign to their protocols, for example 3306 for MySQL or 5432 for PostgreSQL. Ports 49152 to 65535 are dynamic or private, the pool from which clients take temporary source ports.

Searching

Type a port number, a service name such as ssh or postgresql, or a range. The quick buttons offer 22, 53, 80, 443, 3306, 5432, 3389 and 51820. For a number, the page states which range it belongs to and lists each registry entry: the service name, the protocols (such as TCP and UDP) and the IANA description. A word is matched against service names and descriptions. The registry contains 7,152 entries in total.

What a registered port does and does not tell you

The registry records which port a protocol is meant to use. It does not know what runs on a particular machine. A web server on 8443, a database exposed on an unusual port, or malware on port 443 all exist. Conversely, a registered port with nothing listening is just closed. Treat the lookup as the first hint when reading a log, then confirm with the service banner or process list. Unassigned ports can be used freely on a private network but may collide with another application.

A worked example

Search 5432. The page says that 5432 is a registered port in the range 1024 to 49151, and lists one entry: service postgresql, protocols TCP, UDP, description PostgreSQL Database. A firewall rule that allows 5432 from the Internet therefore exposes a database server, which is rarely intended. Searching 51820, the port WireGuard uses by default, finds no registry entry: it lies in the registered range but nobody has registered it, a reminder that a customary port and an assigned one are different things (see the WireGuard Config Generator).

Limits

The data is a snapshot of the IANA registry and is updated with the site, so a very recent assignment may be missing. Many popular services use ports that were never formally registered, or share a registered number with another protocol. The page does not scan your network, test whether a port is open or send any request. Capture filters for specific ports are built by the Wireshark Filter Builder.

Ports worth recognising

A short list covers most logs: 22 for SSH, 25 for mail transfer between servers, 53 for DNS, 80 for HTTP, 123 for the time protocol NTP, 161 for SNMP, 443 for HTTPS, 514 over UDP for syslog, 3306 for MySQL and MariaDB, 3389 for Remote Desktop and 5432 for PostgreSQL. A scan that shows several database or remote-administration ports open on a server that should only publish a website is a configuration problem worth fixing before anyone else finds it.

Related tools

• Wireshark Filter Builder filters traffic by port.
• TCP Flags Decoder explains the segments that open and close connections to these ports.
• WireGuard Config Generator uses UDP 51820 by default.
• SRV Record Lookup finds the host and port of a service published in DNS.