Subnet and PortsPort 22: SSH
Encrypted remote login, command execution and file transfer (SFTP).
Registry entry
| Port | Protocols | Registered name | IANA description | Assignee | Reference | Note |
|---|---|---|---|---|---|---|
| 22 | tcp, udp, sctp | ssh | The Secure Shell (SSH) Protocol | n/a | [RFC 4251] | Defined TXT keys: u=<username> p=<password> |
What it is used for
Encrypted remote login, command execution and file transfer (SFTP).
The risk
It is constantly probed by password-guessing programs.
What to do
Use key-based login, disable password login, restrict by address, and keep it patched.
In the registry
Port 22 is a system port (0 to 1023), the range for standard services. The registry lists one service for this number. Its main entry is ssh, "The Secure Shell (SSH) Protocol", registered for tcp, udp, sctp. IANA adds a note: "Defined TXT keys: u=<username> p=<password>".
How to find out whether it is open on your computer
On your own computer or server, ask the operating system which programs are listening for connections, and look for port 22 in the list. If a program you do not recognise listens on it, find out what it is before you close it. From outside, test only networks that you own or have permission to test: scanning other people's networks can be treated as an attack.
Is port 22 safe to leave open?
It depends on what is listening and who can reach it. Open only what you need, restrict by address where possible, keep the software updated, and use encryption and strong authentication. The advice above applies to this port.
Does the registered name prove what runs on port 22?
No. Programs can use any port. The registry tells you what the number was reserved for.
This is an independent guide. It is not connected with IANA, the IETF or any network equipment maker. Address and port data come from the IANA registries as fetched on 14 November 2026; RFC texts were read from rfc-editor.org. Check the originals for anything you rely on.