Port 6243 (jeol-nsdtp-3, jeol-nsddp-3)

IANA assigns port 6243 to jeol-nsdtp-3, jeol-nsddp-3: JEOL Network Services Data Transport Protocol 3.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

jeol-nsdtp-3 TCP JEOL Network Services Data Transport Protocol 3 Kevin Wellwood -

jeol-nsddp-3 UDP JEOL Network Services Dynamic Discovery Protocol 3 Kevin Wellwood -

Registry dates for this port: registered 2008-04-17.

Linux: is anything listening on TCP 6243?

sudo ss -tlnp 'sport = :6243'

Linux: UDP 6243

sudo ss -ulnp 'sport = :6243'

Linux / macOS: which process owns the port

sudo lsof -nP -i :6243

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':6243 '

Windows (Command Prompt)

netstat -ano | findstr :6243

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 6243 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 6243

From Windows

Test-NetConnection HOST -Port 6243

UDP probe (no reply does not prove it is closed)

nc -vzu -w 5 HOST 6243

ufw

sudo ufw deny 6243/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 6243 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 6243 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 6243' -Direction Inbound -Protocol TCP -LocalPort 6243 -Action Block

ufw

sudo ufw deny 6243/udp

iptables

sudo iptables -A INPUT -p udp --dport 6243 -j DROP

nftables

sudo nft add rule inet filter input udp dport 6243 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 6243' -Direction Inbound -Protocol UDP -LocalPort 6243 -Action Block

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.