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Port 21010 (notezilla-lan)

IANA assigns port 21010 to notezilla-lan: Notezilla.Lan Server.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
notezilla-lan TCP Notezilla.Lan Server Conceptworld Corporation -

Registry dates for this port: registered 2013-08-20.

Check what is listening on port 21010

Linux: is anything listening on TCP 21010?
sudo ss -tlnp 'sport = :21010'
Linux / macOS: which process owns the port
sudo lsof -nP -i :21010
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':21010 '
Windows (Command Prompt)
netstat -ano | findstr :21010
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 21010 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 21010
From Windows
Test-NetConnection HOST -Port 21010

Block port 21010 in the firewall

ufw
sudo ufw deny 21010/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 21010 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 21010 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 21010' -Direction Inbound -Protocol TCP -LocalPort 21010 -Action Block

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