Port 22: SSH
Port 22 is SSH, the encrypted remote command line used to manage servers and devices.
What runs on port 22
OpenSSH and similar servers listen on TCP 22 to give a remote shell, file transfer (SFTP, SCP) and tunnelling. It replaced telnet in the late 1990s because it encrypts everything, including the password. It is the standard way to administer Linux servers, network gear and cloud machines.
On a home network
NAS boxes (Synology, QNAP), Raspberry Pis, OpenWrt and MikroTik routers, Home Assistant with the SSH add-on, and Macs with Remote Login turned on can all listen on 22. Most consumer routers, phones and TVs do not.
If port 22 is reachable from the internet
SSH on the internet is normal for servers and reasonably safe when it uses key-based login and is kept up to date. It is also one of the most brute-forced services on the internet: any address with 22 open receives password guesses within minutes, around the clock. On a home NAS or Pi with a password login, exposure is a real risk; if you need remote access, a VPN is usually the better answer.
How to check whether it is open on your network
Check your router's port forwarding list for any rule pointing at 22, and look at your NAS or Pi settings for SSH. RECON's Port Scan will show which devices on your LAN have 22 open.
To find out whether port 22 is open on something in your home, and whether the internet can reach it, the app scans your Wi-Fi from your phone and checks your public address from the outside. It says what it checked and what it could not. Get RECON for iPhone — one-time purchase, no account, nothing leaves the device.