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// Other services

Port 675: DCTP

Port 675 is assigned by IANA to dctp (DCTP).

675

How dctp works

Other services
client:675dctpresponse client:675dctpresponse

The client sends a request to port 675 and the dctp 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 675 dangerous?

We have no specific security note for port 675. 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 675

ServicePortTransportDescriptionReferenceUpdated
dctp 675 TCP, UDP DCTP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 675, and is it reachable?

Linux

sudo ss -ltnup 'sport = :675'      # process listening on 675
sudo lsof -nP -i :675

macOS

sudo lsof -nP -i :675

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 675 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 675
netstat -ano | findstr :675

From another machine

nmap -p 675 -sV <host>
sudo nmap -sU -p 675 <host>
nc -zv <host> 675

Block it in the firewall

sudo ufw deny 675/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 675" -Direction Inbound -LocalPort 675 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 675 used for?

Port 675 is assigned by IANA to dctp (DCTP).

Is port 675 TCP or UDP?

Port 675 is registered for TCP and UDP.

Is it safe to open port 675?

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 675 is open?

On Linux run "ss -ltnup 'sport = :675'", on macOS "lsof -nP -i :675", and on Windows "netstat -ano | findstr :675" to see the local process. From another machine, "nmap -p 675 <host>" shows whether it is reachable.

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