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Port 3969 (landmarks)

IANA assigns port 3969 to landmarks: Landmark Messages.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
landmarks TCP Landmark Messages Petri Rauhala -
landmarks UDP Landmark Messages Petri Rauhala -

Registry dates for this port: registered 2005-08.

Check what is listening on port 3969

Linux: is anything listening on TCP 3969?
sudo ss -tlnp 'sport = :3969'
Linux: UDP 3969
sudo ss -ulnp 'sport = :3969'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3969
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3969 '
Windows (Command Prompt)
netstat -ano | findstr :3969
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3969 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3969
From Windows
Test-NetConnection HOST -Port 3969
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3969

Block port 3969 in the firewall

ufw
sudo ufw deny 3969/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3969 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3969 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3969' -Direction Inbound -Protocol TCP -LocalPort 3969 -Action Block
ufw
sudo ufw deny 3969/udp
iptables
sudo iptables -A INPUT -p udp --dport 3969 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3969 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3969' -Direction Inbound -Protocol UDP -LocalPort 3969 -Action Block

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