Internet-Security.com TCP port 19 details

Port 19/TCP is used by the Character Generator Protocol (CHARGEN, RFC 864).
It is implemented by classic inetd/xinetd services on Unix systems, such as the xinetd “chargen-stream” service in Red Hat/CentOS and the chargen entry in Debian/Ubuntu’s openbsd-inetd or inetutils-inetd packages.
Microsoft Windows provided a CHARGEN server via the optional “Simple TCP/IP Services” feature in Windows XP and Windows Server 2003/2008, which listens on TCP 19.
Network devices like Cisco routers expose CHARGEN on TCP 19 when the IOS “service tcp-small-servers” option is enabled.
Port 19 is frequently abused in DDoS reflection/amplification attacks (notably via UDP CHARGEN) and in legacy echo–chargen loop attacks, so administrators typically disable it.

TCP 19