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// Other services

Port 15363: 3Link Negotiation

Port 15363 is assigned by IANA to 3link (3Link Negotiation).

15363

How 3link works

Other services
client:153633linkresponse client:153633linkresponse

The client sends a request to port 15363 and the 3link 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 15363 dangerous?

We have no specific security note for port 15363. 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 15363

ServicePortTransportDescriptionReferenceUpdated
3link 15363 TCP, UDP 3Link Negotiation - 2003-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 15363, and is it reachable?

Linux

sudo ss -ltnup 'sport = :15363'      # process listening on 15363
sudo lsof -nP -i :15363

macOS

sudo lsof -nP -i :15363

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 15363 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 15363
netstat -ano | findstr :15363

From another machine

nmap -p 15363 -sV <host>
sudo nmap -sU -p 15363 <host>
nc -zv <host> 15363

Block it in the firewall

sudo ufw deny 15363/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 15363" -Direction Inbound -LocalPort 15363 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 15363 used for?

Port 15363 is assigned by IANA to 3link (3Link Negotiation).

Is port 15363 TCP or UDP?

Port 15363 is registered for TCP and UDP.

Is it safe to open port 15363?

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 15363 is open?

On Linux run "ss -ltnup 'sport = :15363'", on macOS "lsof -nP -i :15363", and on Windows "netstat -ano | findstr :15363" to see the local process. From another machine, "nmap -p 15363 <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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