CyberHunter
Local dataset, no network
// Other services

Port 3616: cd3o Control Protocol

Port 3616 is assigned by IANA to cd3o-protocol (cd3o Control Protocol).

3616

How cd3o-protocol works

Other services
client:3616cd3o-protocolresponse client:3616cd3o-protocolresponse

The client sends a request to port 3616 and the cd3o-protocol 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
Registered (1024-49151)
Category
Other services
01 Security

Is port 3616 dangerous?

We have no specific security note for port 3616. 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 3616

ServicePortTransportDescriptionReferenceUpdated
cd3o-protocol 3616 TCP, UDP cd3o Control Protocol - 2002-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 3616, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3616'      # process listening on 3616
sudo lsof -nP -i :3616

macOS

sudo lsof -nP -i :3616

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3616 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3616
netstat -ano | findstr :3616

From another machine

nmap -p 3616 -sV <host>
sudo nmap -sU -p 3616 <host>
nc -zv <host> 3616

Block it in the firewall

sudo ufw deny 3616/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3616" -Direction Inbound -LocalPort 3616 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3616 used for?

Port 3616 is assigned by IANA to cd3o-protocol (cd3o Control Protocol).

Is port 3616 TCP or UDP?

Port 3616 is registered for TCP and UDP.

Is it safe to open port 3616?

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 3616 is open?

On Linux run "ss -ltnup 'sport = :3616'", on macOS "lsof -nP -i :3616", and on Windows "netstat -ano | findstr :3616" to see the local process. From another machine, "nmap -p 3616 <host>" shows whether it is reachable.

05 Related
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