HTTPfy

Port 19 (chargen)

IANA assigns port 19 to chargen: Character Generator.

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

IANA assignment

Service nameProtoDescriptionAssigneeReference
chargen TCP Character Generator - -
chargen UDP Character Generator - -

Check what is listening on port 19

Linux: is anything listening on TCP 19?
sudo ss -tlnp 'sport = :19'
Linux: UDP 19
sudo ss -ulnp 'sport = :19'
Linux / macOS: which process owns the port
sudo lsof -nP -i :19
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':19 '
Windows (Command Prompt)
netstat -ano | findstr :19
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 19 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 19
From Windows
Test-NetConnection HOST -Port 19
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 19

Block port 19 in the firewall

ufw
sudo ufw deny 19/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 19 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 19 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 19' -Direction Inbound -Protocol TCP -LocalPort 19 -Action Block
ufw
sudo ufw deny 19/udp
iptables
sudo iptables -A INPUT -p udp --dport 19 -j DROP
nftables
sudo nft add rule inet filter input udp dport 19 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 19' -Direction Inbound -Protocol UDP -LocalPort 19 -Action Block

Related ports

17qotd18msp20FTP (data, active mode)21FTP (control)

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