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// Other services

Port 511: PassGo

Port 511 is assigned by IANA to passgo (PassGo).

511

How passgo works

Other services
client:511passgoresponse client:511passgoresponse

The client sends a request to port 511 and the passgo service answers.

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
Other services
01 Security

Is port 511 dangerous?

We have no specific security note for port 511. Its risk depends on the program actually listening on it. General advice for other services services:

  • Close the port if nothing on the host needs it.
  • Identify the process that listens on it (commands below) before opening it in a firewall.
  • Expose a service only to the networks that use it.
02 Registry

IANA registry entries for port 511

ServicePortTransportDescriptionReferenceUpdated
passgo 511 TCP, UDP PassGo - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 511, and is it reachable?

Linux

sudo ss -ltnup 'sport = :511'      # process listening on 511
sudo lsof -nP -i :511

macOS

sudo lsof -nP -i :511

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 511 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 511
netstat -ano | findstr :511

From another machine

nmap -p 511 -sV <host>
sudo nmap -sU -p 511 <host>
nc -zv <host> 511

Block it in the firewall

sudo ufw deny 511/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 511" -Direction Inbound -LocalPort 511 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 511 used for?

Port 511 is assigned by IANA to passgo (PassGo).

Is port 511 TCP or UDP?

Port 511 is registered for TCP and UDP.

Is it safe to open port 511?

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. Close the port if nothing on the host needs it.

How do I check if port 511 is open?

On Linux run "ss -ltnup 'sport = :511'", on macOS "lsof -nP -i :511", and on Windows "netstat -ano | findstr :511" to see the local process. From another machine, "nmap -p 511 <host>" shows whether it is reachable.

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