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// Other services

Port 4851: Apache Derby Replication

Port 4851 is assigned by IANA to derby-repli (Apache Derby Replication).

4851

How derby-repli works

Other services
client:4851derby-repliresponse client:4851derby-repliresponse

The client sends a request to port 4851 and the derby-repli 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 4851 dangerous?

We have no specific security note for port 4851. 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 4851

ServicePortTransportDescriptionReferenceUpdated
derby-repli 4851 TCP, UDP Apache Derby Replication - 2008-02-27

// source: IANA service name and port number registry

03 Check it

Which program uses port 4851, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4851'      # process listening on 4851
sudo lsof -nP -i :4851

macOS

sudo lsof -nP -i :4851

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4851 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4851
netstat -ano | findstr :4851

From another machine

nmap -p 4851 -sV <host>
sudo nmap -sU -p 4851 <host>
nc -zv <host> 4851

Block it in the firewall

sudo ufw deny 4851/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4851" -Direction Inbound -LocalPort 4851 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4851 used for?

Port 4851 is assigned by IANA to derby-repli (Apache Derby Replication).

Is port 4851 TCP or UDP?

Port 4851 is registered for TCP and UDP.

Is it safe to open port 4851?

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 4851 is open?

On Linux run "ss -ltnup 'sport = :4851'", on macOS "lsof -nP -i :4851", and on Windows "netstat -ano | findstr :4851" to see the local process. From another machine, "nmap -p 4851 <host>" shows whether it is reachable.

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