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// Network services

Port 6241: JEOL Network Services Dynamic Discovery Protocol 1

Port 6241 is assigned by IANA to jeol-nsddp-1 (JEOL Network Services Dynamic Discovery Protocol 1), jeol-nsdtp-1 (JEOL Network Services Data Transport Protocol 1).

6241

How jeol-nsddp-1 works

Network services
client:6241jeol-nsddp-1response client:6241jeol-nsddp-1response

The client sends a request to port 6241 and the jeol-nsddp-1 service answers.

Transport
UDP · TCP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned2 registered services
Range
Registered (1024-49151)
Category
Network services
01 Security

Is port 6241 dangerous?

We have no specific security note for port 6241. Its risk depends on the program actually listening on it. General advice for network services services:

  • Answer only the networks that need the service (no open resolvers, relays or reflectors).
  • UDP services can be abused for DDoS amplification: rate-limit or block them at the edge.
  • Disable legacy test services that have no use in production.
02 Registry

IANA registry entries for port 6241

ServicePortTransportDescriptionReferenceUpdated
jeol-nsddp-1 6241 UDP JEOL Network Services Dynamic Discovery Protocol 1 - 2008-04-17
jeol-nsdtp-1 6241 TCP JEOL Network Services Data Transport Protocol 1 - 2008-04-17

// source: IANA service name and port number registry

03 Check it

Which program uses port 6241, and is it reachable?

Linux

sudo ss -ltnup 'sport = :6241'      # process listening on 6241
sudo lsof -nP -i :6241

macOS

sudo lsof -nP -i :6241

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6241 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 6241
netstat -ano | findstr :6241

From another machine

nmap -p 6241 -sV <host>
sudo nmap -sU -p 6241 <host>
nc -zv <host> 6241

Block it in the firewall

sudo ufw deny 6241/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 6241" -Direction Inbound -LocalPort 6241 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 6241 used for?

Port 6241 is assigned by IANA to jeol-nsddp-1 (JEOL Network Services Dynamic Discovery Protocol 1), jeol-nsdtp-1 (JEOL Network Services Data Transport Protocol 1).

Is port 6241 TCP or UDP?

Port 6241 is registered for UDP and TCP.

Is it safe to open port 6241?

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. Answer only the networks that need the service (no open resolvers, relays or reflectors).

How do I check if port 6241 is open?

On Linux run "ss -ltnup 'sport = :6241'", on macOS "lsof -nP -i :6241", and on Windows "netstat -ano | findstr :6241" to see the local process. From another machine, "nmap -p 6241 <host>" shows whether it is reachable.

05 Related
:53 DNS tcp · udp · moderate risk :135 MS RPC tcp · udp · high risk :123 NTP udp · tcp · moderate risk :67 DHCP server udp · tcp · moderate risk :111 rpcbind tcp · udp · high risk :9100 Raw printing (JetDirect) tcp · udp · high risk :631 IPP / CUPS tcp · udp · high risk :5353 mDNS udp · tcp · moderate risk

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