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// Other services

Port 3645: Cyc

Port 3645 is assigned by IANA to cyc (Cyc).

3645

How cyc works

Other services
client:3645cycresponse client:3645cycresponse

The client sends a request to port 3645 and the cyc 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 3645 dangerous?

We have no specific security note for port 3645. 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 3645

ServicePortTransportDescriptionReferenceUpdated
cyc 3645 TCP, UDP Cyc - 2003-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 3645, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3645'      # process listening on 3645
sudo lsof -nP -i :3645

macOS

sudo lsof -nP -i :3645

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3645 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3645
netstat -ano | findstr :3645

From another machine

nmap -p 3645 -sV <host>
sudo nmap -sU -p 3645 <host>
nc -zv <host> 3645

Block it in the firewall

sudo ufw deny 3645/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3645" -Direction Inbound -LocalPort 3645 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3645 used for?

Port 3645 is assigned by IANA to cyc (Cyc).

Is port 3645 TCP or UDP?

Port 3645 is registered for TCP and UDP.

Is it safe to open port 3645?

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 3645 is open?

On Linux run "ss -ltnup 'sport = :3645'", on macOS "lsof -nP -i :3645", and on Windows "netstat -ano | findstr :3645" to see the local process. From another machine, "nmap -p 3645 <host>" shows whether it is reachable.

05 Related
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