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Port 541 (uucp-rlogin)

IANA assigns port 541 to uucp-rlogin.

Well-known (system) port, 0-1023 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
uucp-rlogin TCP uucp-rlogin Stuart Lynne -
uucp-rlogin UDP uucp-rlogin Stuart Lynne -

Check what is listening on port 541

Linux: is anything listening on TCP 541?
sudo ss -tlnp 'sport = :541'
Linux: UDP 541
sudo ss -ulnp 'sport = :541'
Linux / macOS: which process owns the port
sudo lsof -nP -i :541
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':541 '
Windows (Command Prompt)
netstat -ano | findstr :541
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 541 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 541
From Windows
Test-NetConnection HOST -Port 541
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 541

Block port 541 in the firewall

ufw
sudo ufw deny 541/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 541 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 541 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 541' -Direction Inbound -Protocol TCP -LocalPort 541 -Action Block
ufw
sudo ufw deny 541/udp
iptables
sudo iptables -A INPUT -p udp --dport 541 -j DROP
nftables
sudo nft add rule inet filter input udp dport 541 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 541' -Direction Inbound -Protocol UDP -LocalPort 541 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.