CyberHunter
Local dataset, no network
// Other services

Port 641: repcmd

Port 641 is assigned by IANA to repcmd (repcmd).

641

How repcmd works

Other services
client:641repcmdresponse client:641repcmdresponse

The client sends a request to port 641 and the repcmd 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 641 dangerous?

We have no specific security note for port 641. 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 641

ServicePortTransportDescriptionReferenceUpdated
repcmd 641 TCP, UDP repcmd - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 641, and is it reachable?

Linux

sudo ss -ltnup 'sport = :641'      # process listening on 641
sudo lsof -nP -i :641

macOS

sudo lsof -nP -i :641

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 641 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 641
netstat -ano | findstr :641

From another machine

nmap -p 641 -sV <host>
sudo nmap -sU -p 641 <host>
nc -zv <host> 641

Block it in the firewall

sudo ufw deny 641/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 641" -Direction Inbound -LocalPort 641 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 641 used for?

Port 641 is assigned by IANA to repcmd (repcmd).

Is port 641 TCP or UDP?

Port 641 is registered for TCP and UDP.

Is it safe to open port 641?

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 641 is open?

On Linux run "ss -ltnup 'sport = :641'", on macOS "lsof -nP -i :641", and on Windows "netstat -ano | findstr :641" to see the local process. From another machine, "nmap -p 641 <host>" shows whether it is reachable.

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