How to start systemd services on incoming network traffic (XBMC example)

Introduction

Systemd is a system and service manager which provides a neat and easy way to organize and start your services on Linux. Only recently I found out you can use .socket files to start services on incoming network traffic.

Usage with XBMC and XBMC Remote

For example you can use a .socket file to conveniently start xbmc when you connect via the XBMC Remote App. See the following .socket file:

#/etc/systemd/system/xbmcnet.socket
#You might have to use the Service= and Accept=no options if the service name differs from the socket name
[Unit]
Conflicts=xbmcnet.service

[Socket]
ListenStream=8080
#This is the tcp port we listen to traffic to, set to the port you have set in xbmc->settings->network http control port

[Install]
WantedBy=sockets.target

And the matching .service file:

#/etc/systemd/system/xbmcnet.service
#See comments for the xbmcnet.socket file above!
[Unit]
Description=Launch XBMC on main display - oneshot

[Service]
PermissionsStartOnly=true
User = xbmc
Group = xbmc
Type=oneshot
Nice=-1
ExecStart = /usr/bin/xbmc-standalone -l /run/lirc/lircd
ExecStartPost = /usr/bin/bash -c "sleep 10 && systemctl start xbmcnet.socket"
#The sleep is needed because sometimes you are too slow with exiting the xbmc remote app and the traffic might start the service again immediately

[Install]
WantedBy=multi-user.target

Now you only need to start/enable the socket file and everything should be good to go!

systemctl enable xbmcnet.socket
systemctl start xbmcnet.socket