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// Other services

Port 13821: DSMCC Download Protocol

Port 13821 is assigned by IANA to dsmcc-download (DSMCC Download Protocol).

13821

How dsmcc-download works

Other services
client:13821dsmcc-downloadresponse client:13821dsmcc-downloadresponse

The client sends a request to port 13821 and the dsmcc-download 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 13821 dangerous?

We have no specific security note for port 13821. 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 13821

ServicePortTransportDescriptionReferenceUpdated
dsmcc-download 13821 TCP, UDP DSMCC Download Protocol ISO/IEC 13818-6 MPEG-2 DSM-CC -

// source: IANA service name and port number registry

03 Check it

Which program uses port 13821, and is it reachable?

Linux

sudo ss -ltnup 'sport = :13821'      # process listening on 13821
sudo lsof -nP -i :13821

macOS

sudo lsof -nP -i :13821

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 13821 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 13821
netstat -ano | findstr :13821

From another machine

nmap -p 13821 -sV <host>
sudo nmap -sU -p 13821 <host>
nc -zv <host> 13821

Block it in the firewall

sudo ufw deny 13821/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 13821" -Direction Inbound -LocalPort 13821 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 13821 used for?

Port 13821 is assigned by IANA to dsmcc-download (DSMCC Download Protocol).

Is port 13821 TCP or UDP?

Port 13821 is registered for TCP and UDP.

Is it safe to open port 13821?

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 13821 is open?

On Linux run "ss -ltnup 'sport = :13821'", on macOS "lsof -nP -i :13821", and on Windows "netstat -ano | findstr :13821" to see the local process. From another machine, "nmap -p 13821 <host>" shows whether it is reachable.

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