Super Servers

Definition

• Binds passive sockets on ports
• Spawns active sockets upon connection and launches a given script or binary
• STDIN and STDOUT are bound to the opened socket

Examples

• inetd
• xinetd
• systemd

inetd example

 /etc/inetd.conf

telnet  stream  tcp6    nowait  root    /usr/sbin/telnetd

 /etc/services should contain

telnet          23/tcp

Systemd example

/etc/systemd/system/echo-server.socket

[Socket] ListenStream=8888

/etc/systemd/system/echo-server.service

[Service]
ExecStart=/home/kill/.rvm/bin/ruby-1.9.2-p290 /home/kill/bin/echo-server.rb
User=kill
StandardOutput=syslog
StandardError=syslog

External content

• On-demand container activation: https://developer.atlassian.com/blog/2015/03/docker-systemd-socket-activation/ 
• http://ku1ik.com/2012/01/21/systemd-socket-activation-and-ruby.html 
• Inetd example: https://www.freebsd.org/doc/handbook/network-inetd.html