[Unit]
Description=MQTT v3.1 message broker

# If mosquitto is not cofigured to listen on VPN interface.
After=network.target

# If you are listening on VPN interface, instruct systemd that it should wait 
# until VPN service is started up.
#After=network.target openvpn-server@buben-vps.service
#Wants=network.target openvpn-server@buben-vps.service
 
[Service]
Type=simple
ExecStart=/usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
Restart=always
 
[Install]
WantedBy=multi-user.target