Running as a socket‐activated service with systemd

opera-proxy.service:

[Unit]
Description=Opera VPN
Documentation=https://github.com/Snawoot/opera-proxy/
After=network.target network-online.target
Requires=network-online.target
BindsTo=proxy2opera-proxy.service

[Service]
EnvironmentFile=/opt/opera-proxy/opera-proxy.conf
ExecStart=/opt/opera-proxy/opera-proxy $OPTIONS
TimeoutStopSec=5s
LimitNOFILE=1048576
LimitNPROC=512
PrivateTmp=true
ProtectSystem=full

[Install]
WantedBy=default.target

proxy2opera-proxy.service:

[Unit]
Requires=opera-proxy.service
After=opera-proxy.service
Requires=proxy2opera-proxy.socket
After=proxy2opera-proxy.socket
BindsTo=opera-proxy.service

[Service]
Type=notify
ExecStart=/usr/lib/systemd/systemd-socket-proxyd 127.0.0.1:18081 --exit-idle-time=600

proxy2opera-proxy.socket:

[Socket]
ListenStream=18080

[Install]
WantedBy=sockets.target

opera-proxy.conf:

OPTIONS=-bind-address 127.0.0.1:18081