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// Other services

Port 3904: Arnet Omnilink Port

Port 3904 is assigned by IANA to omnilink-port (Arnet Omnilink Port).

3904

How omnilink-port works

Other services
client:3904omnilink-portresponse client:3904omnilink-portresponse

The client sends a request to port 3904 and the omnilink-port 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 3904 dangerous?

We have no specific security note for port 3904. 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 3904

ServicePortTransportDescriptionReferenceUpdated
omnilink-port 3904 TCP, UDP Arnet Omnilink Port - 2003-10

// source: IANA service name and port number registry

03 Check it

Which program uses port 3904, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3904'      # process listening on 3904
sudo lsof -nP -i :3904

macOS

sudo lsof -nP -i :3904

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3904 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3904
netstat -ano | findstr :3904

From another machine

nmap -p 3904 -sV <host>
sudo nmap -sU -p 3904 <host>
nc -zv <host> 3904

Block it in the firewall

sudo ufw deny 3904/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3904" -Direction Inbound -LocalPort 3904 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3904 used for?

Port 3904 is assigned by IANA to omnilink-port (Arnet Omnilink Port).

Is port 3904 TCP or UDP?

Port 3904 is registered for TCP and UDP.

Is it safe to open port 3904?

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 3904 is open?

On Linux run "ss -ltnup 'sport = :3904'", on macOS "lsof -nP -i :3904", and on Windows "netstat -ano | findstr :3904" to see the local process. From another machine, "nmap -p 3904 <host>" shows whether it is reachable.

05 Related
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