CyberHunter
Local dataset, no network
// Other services

Port 3651: XRPC Registry

Port 3651 is assigned by IANA to xrpc-registry (XRPC Registry).

3651

How xrpc-registry works

Other services
client:3651xrpc-registryresponse client:3651xrpc-registryresponse

The client sends a request to port 3651 and the xrpc-registry 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 3651 dangerous?

We have no specific security note for port 3651. 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 3651

ServicePortTransportDescriptionReferenceUpdated
xrpc-registry 3651 TCP, UDP XRPC Registry - 2003-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 3651, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3651'      # process listening on 3651
sudo lsof -nP -i :3651

macOS

sudo lsof -nP -i :3651

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3651 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3651
netstat -ano | findstr :3651

From another machine

nmap -p 3651 -sV <host>
sudo nmap -sU -p 3651 <host>
nc -zv <host> 3651

Block it in the firewall

sudo ufw deny 3651/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3651" -Direction Inbound -LocalPort 3651 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3651 used for?

Port 3651 is assigned by IANA to xrpc-registry (XRPC Registry).

Is port 3651 TCP or UDP?

Port 3651 is registered for TCP and UDP.

Is it safe to open port 3651?

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 3651 is open?

On Linux run "ss -ltnup 'sport = :3651'", on macOS "lsof -nP -i :3651", and on Windows "netstat -ano | findstr :3651" to see the local process. From another machine, "nmap -p 3651 <host>" shows whether it is reachable.

05 Related
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp

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