CyberHunter
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// Other services

Port 205: AppleTalk Unused

Port 205 is assigned by IANA to at-5 (AppleTalk Unused).

205

How at-5 works

Other services
client:205at-5response client:205at-5response

The client sends a request to port 205 and the at-5 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 205 dangerous?

We have no specific security note for port 205. 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 205

ServicePortTransportDescriptionReferenceUpdated
at-5 205 TCP, UDP AppleTalk Unused - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 205, and is it reachable?

Linux

sudo ss -ltnup 'sport = :205'      # process listening on 205
sudo lsof -nP -i :205

macOS

sudo lsof -nP -i :205

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 205 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 205
netstat -ano | findstr :205

From another machine

nmap -p 205 -sV <host>
sudo nmap -sU -p 205 <host>
nc -zv <host> 205

Block it in the firewall

sudo ufw deny 205/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 205" -Direction Inbound -LocalPort 205 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 205 used for?

Port 205 is assigned by IANA to at-5 (AppleTalk Unused).

Is port 205 TCP or UDP?

Port 205 is registered for TCP and UDP.

Is it safe to open port 205?

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 205 is open?

On Linux run "ss -ltnup 'sport = :205'", on macOS "lsof -nP -i :205", and on Windows "netstat -ano | findstr :205" to see the local process. From another machine, "nmap -p 205 <host>" shows whether it is reachable.

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