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Port 3544 (teredo)

IANA assigns port 3544 to teredo: Teredo Port.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
teredo TCP Teredo Port - RFC 4380
teredo UDP Teredo Port - RFC 4380

Check what is listening on port 3544

Linux: is anything listening on TCP 3544?
sudo ss -tlnp 'sport = :3544'
Linux: UDP 3544
sudo ss -ulnp 'sport = :3544'
Linux / macOS: which process owns the port
sudo lsof -nP -i :3544
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':3544 '
Windows (Command Prompt)
netstat -ano | findstr :3544
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 3544 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 3544
From Windows
Test-NetConnection HOST -Port 3544
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 3544

Block port 3544 in the firewall

ufw
sudo ufw deny 3544/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 3544 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 3544 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 3544' -Direction Inbound -Protocol TCP -LocalPort 3544 -Action Block
ufw
sudo ufw deny 3544/udp
iptables
sudo iptables -A INPUT -p udp --dport 3544 -j DROP
nftables
sudo nft add rule inet filter input udp dport 3544 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 3544' -Direction Inbound -Protocol UDP -LocalPort 3544 -Action Block

Related ports

3542hacl-monitor3543qftest-lookup3545camac3547symantec-sim

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