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// Other services

Port 223: Certificate Distribution Center

Port 223 is assigned by IANA to cdc (Certificate Distribution Center).

223

How cdc works

Other services
client:223cdcresponse client:223cdcresponse

The client sends a request to port 223 and the cdc 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 223 dangerous?

We have no specific security note for port 223. 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 223

ServicePortTransportDescriptionReferenceUpdated
cdc 223 TCP, UDP Certificate Distribution Center - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 223, and is it reachable?

Linux

sudo ss -ltnup 'sport = :223'      # process listening on 223
sudo lsof -nP -i :223

macOS

sudo lsof -nP -i :223

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 223 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 223
netstat -ano | findstr :223

From another machine

nmap -p 223 -sV <host>
sudo nmap -sU -p 223 <host>
nc -zv <host> 223

Block it in the firewall

sudo ufw deny 223/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 223" -Direction Inbound -LocalPort 223 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 223 used for?

Port 223 is assigned by IANA to cdc (Certificate Distribution Center).

Is port 223 TCP or UDP?

Port 223 is registered for TCP and UDP.

Is it safe to open port 223?

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 223 is open?

On Linux run "ss -ltnup 'sport = :223'", on macOS "lsof -nP -i :223", and on Windows "netstat -ano | findstr :223" to see the local process. From another machine, "nmap -p 223 <host>" shows whether it is reachable.

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