Port 5556 (freeciv)

IANA assigns port 5556 to freeciv: Freeciv gameplay.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference

freeciv TCP Freeciv gameplay Reinier Post and Pau -

freeciv UDP Freeciv gameplay Reinier Post and Pau -

Registry dates for this port: registered 2006-01.

Linux: is anything listening on TCP 5556?

sudo ss -tlnp 'sport = :5556'

Linux: UDP 5556

sudo ss -ulnp 'sport = :5556'

Linux / macOS: which process owns the port

sudo lsof -nP -i :5556

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':5556 '

Windows (Command Prompt)

netstat -ano | findstr :5556

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5556 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 5556

From Windows

Test-NetConnection HOST -Port 5556

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

nc -vzu -w 5 HOST 5556

ufw

sudo ufw deny 5556/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 5556 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 5556 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 5556' -Direction Inbound -Protocol TCP -LocalPort 5556 -Action Block

ufw

sudo ufw deny 5556/udp

iptables

sudo iptables -A INPUT -p udp --dport 5556 -j DROP

nftables

sudo nft add rule inet filter input udp dport 5556 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block UDP 5556' -Direction Inbound -Protocol UDP -LocalPort 5556 -Action Block

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