HTTPfy

Port 30400 (gs-realtime)

IANA assigns port 30400 to gs-realtime: GroundStar RealTime System.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
gs-realtime TCP GroundStar RealTime System INFORM GmbH -

Registry dates for this port: registered 2017-08-10, last modified 2017-12-13.

Check what is listening on port 30400

Linux: is anything listening on TCP 30400?
sudo ss -tlnp 'sport = :30400'
Linux / macOS: which process owns the port
sudo lsof -nP -i :30400
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':30400 '
Windows (Command Prompt)
netstat -ano | findstr :30400
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 30400 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 30400
From Windows
Test-NetConnection HOST -Port 30400

Block port 30400 in the firewall

ufw
sudo ufw deny 30400/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 30400 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 30400 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 30400' -Direction Inbound -Protocol TCP -LocalPort 30400 -Action Block

Related ports

30100rwp30260kingdomsonline30832samsung-disc30939dilithium3

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