HTTPfy

Port 4727 (fcis, fcis-disc)

IANA assigns port 4727 to fcis, fcis-disc: F-Link Client Information Service.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
fcis TCP F-Link Client Information Service - -
fcis-disc UDP F-Link Client Information Service Discovery Makoto Zukawa -

Registry dates for this port: registered 2010-10-15.

Check what is listening on port 4727

Linux: is anything listening on TCP 4727?
sudo ss -tlnp 'sport = :4727'
Linux: UDP 4727
sudo ss -ulnp 'sport = :4727'
Linux / macOS: which process owns the port
sudo lsof -nP -i :4727
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':4727 '
Windows (Command Prompt)
netstat -ano | findstr :4727
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4727 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 4727
From Windows
Test-NetConnection HOST -Port 4727
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 4727

Block port 4727 in the firewall

ufw
sudo ufw deny 4727/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 4727 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 4727 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 4727' -Direction Inbound -Protocol TCP -LocalPort 4727 -Action Block
ufw
sudo ufw deny 4727/udp
iptables
sudo iptables -A INPUT -p udp --dport 4727 -j DROP
nftables
sudo nft add rule inet filter input udp dport 4727 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 4727' -Direction Inbound -Protocol UDP -LocalPort 4727 -Action Block

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Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.