Port 18104 (radpdf)

IANA assigns port 18104 to radpdf: RAD PDF Service.

Registered (user) port, 1024-49151 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference

radpdf TCP RAD PDF Service Christopher Truxaw -

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

Linux: is anything listening on TCP 18104?

sudo ss -tlnp 'sport = :18104'

Linux / macOS: which process owns the port

sudo lsof -nP -i :18104

Older Linux / BSD (net-tools)

sudo netstat -tlnp | grep ':18104 '

Windows (Command Prompt)

netstat -ano | findstr :18104

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 18104 -State Listen | Select LocalAddress,OwningProcess

From another machine

nc -vz -w 5 HOST 18104

From Windows

Test-NetConnection HOST -Port 18104

ufw

sudo ufw deny 18104/tcp

iptables

sudo iptables -A INPUT -p tcp --dport 18104 -j DROP

nftables

sudo nft add rule inet filter input tcp dport 18104 drop

Windows Firewall

New-NetFirewallRule -DisplayName 'Block TCP 18104' -Direction Inbound -Protocol TCP -LocalPort 18104 -Action Block

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