CyberHunter
Local dataset, no network
// Other services

Port 4556: DTN Bundle TCP CL Protocol

Port 4556 is assigned by IANA to dtn-bundle (DTN Bundle TCP CL Protocol).

4556

How dtn-bundle works

Other services
client:4556dtn-bundleresponse client:4556dtn-bundleresponse

The client sends a request to port 4556 and the dtn-bundle service answers.

Transport
TCP · UDP · DCCP
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 4556 dangerous?

We have no specific security note for port 4556. 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 4556

ServicePortTransportDescriptionReferenceUpdated
dtn-bundle 4556 TCP, UDP, DCCP DTN Bundle TCP CL Protocol RFC 9174 2021-02-22

// source: IANA service name and port number registry

03 Check it

Which program uses port 4556, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4556'      # process listening on 4556
sudo lsof -nP -i :4556

macOS

sudo lsof -nP -i :4556

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4556 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4556
netstat -ano | findstr :4556

From another machine

nmap -p 4556 -sV <host>
sudo nmap -sU -p 4556 <host>
nc -zv <host> 4556

Block it in the firewall

sudo ufw deny 4556/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4556" -Direction Inbound -LocalPort 4556 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4556 used for?

Port 4556 is assigned by IANA to dtn-bundle (DTN Bundle TCP CL Protocol).

Is port 4556 TCP or UDP?

Port 4556 is registered for TCP and UDP and DCCP.

Is it safe to open port 4556?

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 4556 is open?

On Linux run "ss -ltnup 'sport = :4556'", on macOS "lsof -nP -i :4556", and on Windows "netstat -ano | findstr :4556" to see the local process. From another machine, "nmap -p 4556 <host>" shows whether it is reachable.

05 Related
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