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Port 21221 (aigairserver)

IANA assigns port 21221 to aigairserver: Services for Air Server.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
aigairserver TCP Services for Air Server AIG S.L. -

Registry dates for this port: registered 2017-03-16.

Check what is listening on port 21221

Linux: is anything listening on TCP 21221?
sudo ss -tlnp 'sport = :21221'
Linux / macOS: which process owns the port
sudo lsof -nP -i :21221
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':21221 '
Windows (Command Prompt)
netstat -ano | findstr :21221
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 21221 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 21221
From Windows
Test-NetConnection HOST -Port 21221

Block port 21221 in the firewall

ufw
sudo ufw deny 21221/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 21221 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 21221 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 21221' -Direction Inbound -Protocol TCP -LocalPort 21221 -Action Block

Related ports

21212trinket-agent21213cohesity-agent21337xahaud21553rdm-tfs

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.