- Close the port if nothing on the host needs it.
- Identify the process that listens on it (commands below) before opening it in a firewall.
- Expose a service only to the networks that use it.
Port 21221: Services for Air Server
Port 21221 is assigned by IANA to aigairserver (Services for Air Server).
21221
How aigairserver works
Other servicesThe client sends a request to port 21221 and the aigairserver service answers.
- Transport
- TCP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- Other services
Is port 21221 dangerous?
We have no specific security note for port 21221. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 21221
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| aigairserver | 21221 | TCP | Services for Air Server | - | 2017-03-16 |
| - | 21221 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 21221, and is it reachable?
Linux
sudo ss -ltnup 'sport = :21221' # process listening on 21221
sudo lsof -nP -i :21221macOS
sudo lsof -nP -i :21221
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 21221 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 21221 netstat -ano | findstr :21221
From another machine
nmap -p 21221 -sV <host> nc -zv <host> 21221
Block it in the firewall
sudo ufw deny 21221/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 21221" -Direction Inbound -LocalPort 21221 -Protocol TCP -Action Block # Windows
What is port 21221 used for?
Port 21221 is assigned by IANA to aigairserver (Services for Air Server).
Is port 21221 TCP or UDP?
Port 21221 is registered for TCP.
Is it safe to open port 21221?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.
How do I check if port 21221 is open?
On Linux run "ss -ltnup 'sport = :21221'", on macOS "lsof -nP -i :21221", and on Windows "netstat -ano | findstr :21221" to see the local process. From another machine, "nmap -p 21221 <host>" shows whether it is reachable.
Other other services ports
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp