HTTPfy

Port 15 (Unassigned [was netstat])

IANA assigns port 15 to Unassigned [was netstat].

Well-known (system) port, 0-1023 TCP

IANA assignment

Service nameProtoDescriptionAssigneeReference
- TCP Unassigned [was netstat] - -

Check what is listening on port 15

Linux: is anything listening on TCP 15?
sudo ss -tlnp 'sport = :15'
Linux / macOS: which process owns the port
sudo lsof -nP -i :15
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':15 '
Windows (Command Prompt)
netstat -ano | findstr :15
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 15 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 15
From Windows
Test-NetConnection HOST -Port 15

Block port 15 in the firewall

ufw
sudo ufw deny 15/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 15 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 15 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 15' -Direction Inbound -Protocol TCP -LocalPort 15 -Action Block

Related ports

11systat13daytime17qotd18msp

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