Install SoftEther VPN Server as systemd service.

install-sevpn-service.sh

sudo tee /lib/systemd/system/vpnserver.service << END
[Unit]
Description=SoftEther VPN Server
After=network.target
[Service]
Type=forking
Environment="TAP=tap_vpn"
Environment="BR=br0"
ExecStartPre=ip tuntap add \$TAP mode tap
ExecStartPre=ip link set \$TAP up
ExecStartPre=ip link set dev \$TAP master \$BR
ExecStartPre=iptables -A FORWARD -i \$BR -o \$BR -j ACCEPT
ExecStart=/usr/local/vpnserver/vpnserver start
ExecStop=/usr/local/vpnserver/vpnserver stop
ExecStopPost=ip link delete \$TAP
ExecStopPost=iptables -D FORWARD -i \$BR -o \$BR -j ACCEPT
[Install]
WantedBy=multi-user.target
END
sudo systemctl daemon-reload

sudo systemctl enable vpnserver.service