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// Remote access

Port 541: uucp-rlogin

Port 541 is assigned by IANA to uucp-rlogin (uucp-rlogin).

541

How uucp-rlogin works

Remote access
terminal:541uucp-rlogin terminal:541uucp-rlogin

The client opens a session to port 541: each command typed is sent to the server, which runs it and returns the output.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
Remote access
01 Security

Is port 541 dangerous?

We have no specific security note for port 541. Its risk depends on the program actually listening on it. General advice for remote access services:

  • Do not expose remote administration directly: use a VPN or a zero-trust access proxy.
  • Require MFA or key-based authentication and lock out brute-force attempts.
  • Log every login and alert on new source addresses.
02 Registry

IANA registry entries for port 541

ServicePortTransportDescriptionReferenceUpdated
uucp-rlogin 541 TCP, UDP uucp-rlogin - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 541, and is it reachable?

Linux

sudo ss -ltnup 'sport = :541'      # process listening on 541
sudo lsof -nP -i :541

macOS

sudo lsof -nP -i :541

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 541 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 541
netstat -ano | findstr :541

From another machine

nmap -p 541 -sV <host>
sudo nmap -sU -p 541 <host>
nc -zv <host> 541

Block it in the firewall

sudo ufw deny 541/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 541" -Direction Inbound -LocalPort 541 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 541 used for?

Port 541 is assigned by IANA to uucp-rlogin (uucp-rlogin).

Is port 541 TCP or UDP?

Port 541 is registered for TCP and UDP.

Is it safe to open port 541?

It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Do not expose remote administration directly: use a VPN or a zero-trust access proxy.

How do I check if port 541 is open?

On Linux run "ss -ltnup 'sport = :541'", on macOS "lsof -nP -i :541", and on Windows "netstat -ano | findstr :541" to see the local process. From another machine, "nmap -p 541 <host>" shows whether it is reachable.

05 Related
:22 SSH tcp · udp · sctp · moderate risk :3389 RDP tcp · udp · critical risk :23 Telnet tcp · udp · critical risk :5900 VNC tcp · udp · critical risk :5985 WinRM (HTTP) tcp · udp · high risk :5986 WinRM (HTTPS) tcp · udp · high risk :10000 Webmin tcp · udp · high risk :89 SU/MIT Telnet Gateway tcp · udp

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