test-modem-fix.sh

#!/bin/bash

# This script is Quectel-specific (AT+QCFG="usbnet" commands) and must only run
# against that modem model. Detect it by the presence of its USB by-id path and
# bail out early — before touching ModemManager — for any other modem.
MODEM_PORT="${1:-/dev/serial/by-id/usb-Android_Android_0000-if03-port0}"

if [ ! -e "$MODEM_PORT" ]; then
    echo "Modem not found at $MODEM_PORT" >&2
    echo "This script only supports the Quectel modem; aborting." >&2
    exit 1
fi

# Stop ModemManager service
echo "Stopping ModemManager..."
sudo systemctl stop ModemManager

# Disable ModemManager to prevent auto-restart
echo "Disabling ModemManager..."
sudo systemctl disable ModemManager

echo "Connecting to modem on $MODEM_PORT..."

# Send AT commands via file descriptor
exec 3<>"$MODEM_PORT"

send_at() {
    echo ">>> $1"
    printf '%s\r' "$1" >&3
    timeout 3 cat <&3 &
    sleep 2
    kill $! 2>/dev/null
    wait $! 2>/dev/null
    echo
}

send_at 'AT+QCFG="usbnet"'
send_at 'AT+QCFG="usbnet",3'
send_at 'AT+QCFG="usbnet"'
send_at 'AT+CFUN=1,1'

exec 3>&-

# Prompt user to restart router
echo ""
echo "================================"
echo "Manual Steps Required:"
echo "1. Power off the Xnergy router"
echo "================================"
read -p "Press Enter after completing the above steps..."

# Re-enable ModemManager
echo "Enabling ModemManager..."
sudo systemctl enable ModemManager

sleep 1

echo "Done"
# Restart device
# echo "Restarting..."
# sudo shutdown -r now