[Unit]
Description=FailureWatt Growatt Modbus RTU->TCP bridge
After=network-online.target
Wants=network-online.target
StartLimitIntervalSec=60
StartLimitBurst=5

[Service]
Type=simple
Environment=DEVICE=/dev/serial/by-id/usb-YOUR_RS485_ADAPTER
Environment=BRIDGE_IP=192.168.1.20
Environment=BRIDGE_PORT=5020

# Important: no unrestricted "fork" here.
# One TCP client is bridged to one serial adapter.
ExecStart=/usr/bin/socat -d -d \
  TCP-LISTEN:${BRIDGE_PORT},bind=${BRIDGE_IP},reuseaddr \
  FILE:${DEVICE},raw,b9600,cs8,parenb=0,cstopb=0

Restart=always
RestartSec=10
TimeoutStopSec=5
KillMode=control-group
SuccessExitStatus=143

User=root
Group=dialout

[Install]
WantedBy=multi-user.target