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// Other services

Port 655: TINC

Port 655 is assigned by IANA to tinc (TINC).

655

How tinc works

Other services
client:655tincresponse client:655tincresponse

The client sends a request to port 655 and the tinc 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 655 dangerous?

We have no specific security note for port 655. 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 655

ServicePortTransportDescriptionReferenceUpdated
tinc 655 TCP, UDP TINC - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 655, and is it reachable?

Linux

sudo ss -ltnup 'sport = :655'      # process listening on 655
sudo lsof -nP -i :655

macOS

sudo lsof -nP -i :655

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 655 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 655
netstat -ano | findstr :655

From another machine

nmap -p 655 -sV <host>
sudo nmap -sU -p 655 <host>
nc -zv <host> 655

Block it in the firewall

sudo ufw deny 655/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 655" -Direction Inbound -LocalPort 655 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 655 used for?

Port 655 is assigned by IANA to tinc (TINC).

Is port 655 TCP or UDP?

Port 655 is registered for TCP and UDP.

Is it safe to open port 655?

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 655 is open?

On Linux run "ss -ltnup 'sport = :655'", on macOS "lsof -nP -i :655", and on Windows "netstat -ano | findstr :655" to see the local process. From another machine, "nmap -p 655 <host>" shows whether it is reachable.

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