Manage dcc-usb-connector auto-stop on removal

connector/99-dcc-usb-connector.rules

@@ -0,0 +1,22 @@
+# Udev rule to auto-start/stop dcc-usb-connector.service when USB device is connected/removed
+#
+# This rule detects when a CH340 USB-to-serial adapter (ID 1a86:7523)
+# is connected/removed on /dev/ttyUSB0, then automatically starts/stops
+# the dcc-usb-connector.service (user systemd service).
+#
+# Installation:
+#   sudo cp 99-dcc-usb-connector.rules /etc/udev/rules.d/
+#   sudo udevadm control --reload-rules
+#   sudo udevadm trigger --subsystem-match=tty
+#
+# Testing:
+#   udevadm test /sys/class/tty/ttyUSB0
+#   udevadm monitor --property --subsystem-match=tty
+#
+# The service will be started when the device is plugged in and stopped
+# when the device is unplugged.
+
+# Match USB device 1a86:7523 on ttyUSB0
+# TAG+="systemd" tells systemd to track this device
+# ENV{SYSTEMD_USER_WANTS} starts the service on "add" and stops it on "remove"
+SUBSYSTEM=="tty", ATTRS{idVendor}=="1a86", ATTRS{idProduct}=="7523", KERNEL=="ttyUSB0", TAG+="systemd", ENV{SYSTEMD_USER_WANTS}="dcc-usb-connector.service"

connector/INSTALL.md

@@ -0,0 +1,345 @@
+# DCC USB-to-Network Bridge Auto-Start Installation
+
+This directory contains configuration files to automatically start the `dcc-usb-connector.service` when a specific USB device (CH340 USB-to-serial adapter, ID `1a86:7523`) is connected to `/dev/ttyUSB0`.
+
+## Overview
+
+The setup uses:
+- **Udev rule** (`99-dcc-usb-connector.rules`) - Detects USB device connection/disconnection
+- **Systemd user service** (`dcc-usb-connector.service`) - Bridges serial port to network port 2560
+- **Installation script** (`install-udev-rule.sh`) - Automated installation helper
+
+When the USB device is plugged in, the service automatically starts. When unplugged, it stops.
+
+## Prerequisites
+
+1. **Operating System**: Linux with systemd and udev
+2. **Required packages**:
+   ```bash
+   sudo dnf install nmap-ncat systemd udev
+   ```
+3. **User permissions**: Your user should be in the `dialout` group:
+   ```bash
+   sudo usermod -a -G dialout $USER
+   # Log out and log back in for changes to take effect
+   ```
+
+## Quick Installation
+
+Run the installation script:
+
+```bash
+./install-udev-rule.sh
+```
+
+This script will:
+- Install the udev rule (requires sudo)
+- Install the systemd user service to `~/.config/systemd/user/`
+- Enable systemd lingering for your user
+- Check for required tools and permissions
+- Provide testing instructions
+
+## Manual Installation
+
+If you prefer to install manually:
+
+### 1. Install the udev rule
+
+```bash
+sudo cp 99-dcc-usb-connector.rules /etc/udev/rules.d/
+sudo udevadm control --reload-rules
+sudo udevadm trigger --subsystem-match=tty
+```
+
+### 2. Install the systemd service
+
+```bash
+mkdir -p ~/.config/systemd/user/
+cp dcc-usb-connector.service ~/.config/systemd/user/
+systemctl --user daemon-reload
+```
+
+### 3. Enable lingering (optional but recommended)
+
+This allows your user services to run even when you're not logged in:
+
+```bash
+sudo loginctl enable-linger $USER
+```
+
+## Verification
+
+### Test the udev rule
+
+```bash
+# Monitor udev events (plug/unplug device while this runs)
+udevadm monitor --property --subsystem-match=tty
+
+# Test udev rule (when device is connected)
+udevadm test /sys/class/tty/ttyUSB0
+```
+
+### Check service status
+
+```bash
+# Check if service is running
+systemctl --user status dcc-usb-connector.service
+
+# View service logs
+journalctl --user -u dcc-usb-connector.service -f
+```
+
+### Test the network bridge
+
+```bash
+# Connect to the bridge
+telnet localhost 2560
+
+# Or using netcat
+nc localhost 2560
+```
+
+## Usage
+
+### Automatic Operation
+
+Once installed, the service will:
+- **Start automatically** when USB device `1a86:7523` is connected to `/dev/ttyUSB0`
+- **Stop automatically** when the device is disconnected
+- Bridge serial communication to network port `2560`
+
+### Manual Control
+
+You can still manually control the service:
+
+```bash
+# Start the service
+systemctl --user start dcc-usb-connector.service
+
+# Stop the service
+systemctl --user stop dcc-usb-connector.service
+
+# Check status
+systemctl --user status dcc-usb-connector.service
+
+# View logs
+journalctl --user -u dcc-usb-connector.service
+```
+
+## How It Works
+
+### Component Interaction
+
+```
+USB Device Connected (1a86:7523 on /dev/ttyUSB0)
+         ↓
+    Udev Rule Triggered
+         ↓
+    Systemd User Service Started
+         ↓
+    stty configures serial port (115200 baud)
+         ↓
+    ncat bridges /dev/ttyUSB0 ↔ TCP port 2560
+         ↓
+    Client apps connect to localhost:2560
+```
+
+### Udev Rule Details
+
+The udev rule (`99-dcc-usb-connector.rules`) matches:
+- **Subsystem**: `tty` (TTY/serial devices)
+- **Vendor ID**: `1a86` (CH340 manufacturer)
+- **Product ID**: `7523` (CH340 serial adapter)
+- **Kernel device**: `ttyUSB0` (specific port)
+
+When matched, it sets `ENV{SYSTEMD_USER_WANTS}="dcc-usb-connector.service"`, telling systemd to start the service.
+
+### Service Configuration
+
+The service (`dcc-usb-connector.service`):
+1. Runs `stty -F /dev/ttyUSB0 -echo 115200` to configure the serial port
+2. Executes `ncat -n -k -l 2560 </dev/ttyUSB0 >/dev/ttyUSB0` to bridge serial ↔ network
+3. Uses `KillMode=mixed` for proper process cleanup
+4. Terminates within 5 seconds when stopped
+5. **Uses `StopWhenUnneeded=yes`** - This ensures the service stops when the device is removed
+
+### Auto-Stop Mechanism
+
+When the USB device is unplugged:
+1. **Udev detects** the removal event
+2. **Systemd removes** the device dependency from the service
+3. **StopWhenUnneeded=yes** tells systemd to automatically stop the service when no longer needed
+4. **Service terminates** gracefully within 5 seconds
+
+This combination ensures clean automatic stop without requiring manual intervention or custom scripts.
+
+## Troubleshooting
+
+### Service doesn't start automatically
+
+1. **Check udev rule is loaded**:
+   ```bash
+   udevadm test /sys/class/tty/ttyUSB0 | grep SYSTEMD_USER_WANTS
+   ```
+   Should show: `ENV{SYSTEMD_USER_WANTS}='dcc-usb-connector.service'`
+
+2. **Check device is recognized**:
+   ```bash
+   lsusb | grep 1a86:7523
+   ls -l /dev/ttyUSB0
+   ```
+
+3. **Verify systemd user instance is running**:
+   ```bash
+   systemctl --user status
+   loginctl show-user $USER | grep Linger
+   ```
+
+### Permission denied on /dev/ttyUSB0
+
+Add your user to the `dialout` group:
+```bash
+sudo usermod -a -G dialout $USER
+# Log out and log back in
+groups  # Verify 'dialout' appears
+```
+
+### Device appears as /dev/ttyUSB1 instead of /dev/ttyUSB0
+
+The udev rule specifically matches `ttyUSB0`. To make it flexible:
+
+Edit `99-dcc-usb-connector.rules` and change:
+```
+KERNEL=="ttyUSB0"
+```
+to:
+```
+KERNEL=="ttyUSB[0-9]*"
+```
+
+Then reload:
+```bash
+sudo udevadm control --reload-rules
+sudo udevadm trigger --subsystem-match=tty
+```
+
+### Service starts but ncat fails
+
+1. **Check ncat is installed**:
+   ```bash
+   which ncat
+   ncat --version
+   ```
+
+2. **Verify serial port works**:
+   ```bash
+   stty -F /dev/ttyUSB0
+   cat /dev/ttyUSB0  # Should not error
+   ```
+
+3. **Check port 2560 is available**:
+   ```bash
+   netstat -tuln | grep 2560
+   # Should be empty if nothing is listening
+   ```
+
+### View detailed logs
+
+```bash
+# Follow service logs in real-time
+journalctl --user -u dcc-usb-connector.service -f
+
+# View all logs for the service
+journalctl --user -u dcc-usb-connector.service
+
+# View with timestamps
+journalctl --user -u dcc-usb-connector.service -o short-iso
+```
+
+## Uninstallation
+
+To remove the auto-start feature:
+
+```bash
+# Remove udev rule
+sudo rm /etc/udev/rules.d/99-dcc-usb-connector.rules
+sudo udevadm control --reload-rules
+sudo udevadm trigger --subsystem-match=tty
+
+# Remove systemd service
+systemctl --user stop dcc-usb-connector.service
+rm ~/.config/systemd/user/dcc-usb-connector.service
+systemctl --user daemon-reload
+
+# (Optional) Disable lingering
+sudo loginctl disable-linger $USER
+```
+
+## Advanced Configuration
+
+### Customize for different USB device
+
+Edit `99-dcc-usb-connector.rules` and change:
+- `ATTRS{idVendor}=="1a86"` - USB vendor ID
+- `ATTRS{idProduct}=="7523"` - USB product ID
+
+Find your device IDs with:
+```bash
+lsusb
+# Output: Bus 001 Device 003: ID 1a86:7523 QinHeng Electronics ...
+#                                   ^^^^:^^^^
+#                                   VID   PID
+```
+
+### Change network port
+
+Edit `dcc-usb-connector.service` and change:
+```
+ExecStart=/usr/bin/bash -c "/usr/bin/ncat -n -k -l 2560 ...
+```
+Replace `2560` with your desired port number.
+
+### Enable auto-restart on failure
+
+Edit `dcc-usb-connector.service` and add under `[Service]`:
+```
+Restart=on-failure
+RestartSec=5
+```
+
+Then reload:
+```bash
+systemctl --user daemon-reload
+```
+
+## Testing Without Physical Device
+
+For development/testing without the actual USB device:
+
+```bash
+# Create a virtual serial port pair
+socat -d -d pty,raw,echo=0 pty,raw,echo=0
+
+# This creates two linked devices, e.g., /dev/pts/3 and /dev/pts/4
+# Update the service to use one of these instead of /dev/ttyUSB0
+```
+
+## References
+
+- [systemd user services](https://www.freedesktop.org/software/systemd/man/systemd.service.html)
+- [udev rules writing](https://www.reactivated.net/writing_udev_rules.html)
+- [ncat documentation](https://nmap.org/ncat/)
+- [DCC++ EX](https://dcc-ex.com/) - The DCC command station software
+
+## License
+
+See the main project LICENSE file.
+
+## Support
+
+For issues specific to the auto-start feature:
+1. Check the troubleshooting section above
+2. Review logs: `journalctl --user -u dcc-usb-connector.service`
+3. Test udev rules: `udevadm test /sys/class/tty/ttyUSB0`
+
+For DCC++ EX or django-ram issues, see the main project documentation.

connector/README.md

@@ -1,17 +1,53 @@
-# Use a container to implement a serial to net bridge
+# DCC Serial-to-Network Bridge
 
-This uses `ncat` from [nmap](https://nmap.org/ncat/) to bridge a serial port to a network port. The serial port is passed to the Podman command (eg. `/dev/ttyACM0`) and the network port is `2560`.
+This directory provides two ways to bridge a serial port to a network port using `ncat` from [nmap](https://nmap.org/ncat/):
+
+1. **Auto-Start with systemd + udev** (Recommended) - Automatically starts/stops when USB device is plugged/unplugged
+2. **Container-based** - Manual control using Podman/Docker
 
 > [!IMPORTANT]
 > Other variants of `nc` or `ncat` may not work as expected.
 
-## Build and run the container
+## Option 1: Auto-Start with systemd + udev (Recommended)
+
+Automatically start the bridge when USB device `1a86:7523` is connected to `/dev/ttyUSB0` and stop it when removed.
+
+### Quick Install
 
 ```bash
-$ podman buil -t dcc/bridge .
+./install-udev-rule.sh
+```
+
+### Features
+- ✅ Auto-start when device connected
+- ✅ Auto-stop when device removed
+- ✅ User-level service (no root needed)
+- ✅ Runs on boot (with lingering enabled)
+
+See [INSTALL.md](INSTALL.md) for detailed documentation.
+
+### Test
+
+```bash
+# Run the test script
+./test-udev-autostart.sh
+
+# Or manually check
+systemctl --user status dcc-usb-connector.service
+telnet localhost 2560
+```
+
+## Option 2: Container-based (Manual)
+
+### Build and run the container
+
+```bash
+$ podman build -t dcc/bridge .
 $ podman run -d --group-add keep-groups --device=/dev/ttyACM0:/dev/arduino -p 2560:2560 --name dcc-bridge dcc/bridge
 ```
 
+### Test
+
 It can be tested with `telnet`:
 
 ```bash

connector/dcc-usb-connector.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=DCC USB-to-Network Bridge Daemon
+After=network.target
+# Device will be available via udev rule, but add condition as safety check
+ConditionPathIsReadWrite=/dev/ttyUSB0
+# Stop this service when the device is no longer needed (removed)
+StopWhenUnneeded=yes
+
+[Service]
+ExecStartPre=/usr/bin/stty -F /dev/ttyUSB0 -echo 115200
+ExecStart=/usr/bin/bash -c "/usr/bin/ncat -n -k -l 2560 </dev/ttyUSB0 >/dev/ttyUSB0"
+KillMode=mixed
+TimeoutStopSec=5
+PrivateTmp=true
+
+[Install]
+WantedBy=default.target

connector/install-udev-rule.sh

@@ -0,0 +1,127 @@
+#!/usr/bin/env bash
+#
+# Installation script for DCC USB-to-Network Bridge auto-start
+#
+# This script installs the udev rule and systemd service to automatically
+# start the dcc-usb-connector.service when USB device 1a86:7523 is connected.
+#
+# Usage:
+#   ./install-udev-rule.sh
+#
+
+set -e
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+# Get the directory where this script is located
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+
+echo -e "${GREEN}DCC USB-to-Network Bridge Auto-Start Installation${NC}"
+echo "=========================================================="
+echo
+
+# Check if running as root (not recommended for systemd user service)
+if [ "$EUID" -eq 0 ]; then
+    echo -e "${YELLOW}Warning: You are running as root.${NC}"
+    echo "This script will install a user systemd service."
+    echo "Please run as a regular user (not with sudo)."
+    echo
+    read -p "Continue anyway? (y/N) " -n 1 -r
+    echo
+    if [[ ! $REPLY =~ ^[Yy]$ ]]; then
+        exit 1
+    fi
+fi
+
+# Check for required files
+echo "Checking required files..."
+if [ ! -f "$SCRIPT_DIR/99-dcc-usb-connector.rules" ]; then
+    echo -e "${RED}Error: 99-dcc-usb-connector.rules not found${NC}"
+    exit 1
+fi
+if [ ! -f "$SCRIPT_DIR/dcc-usb-connector.service" ]; then
+    echo -e "${RED}Error: dcc-usb-connector.service not found${NC}"
+    exit 1
+fi
+echo -e "${GREEN}✓ All required files found${NC}"
+echo
+
+# Install udev rule (requires sudo)
+echo "Installing udev rule..."
+echo "This requires sudo privileges."
+sudo cp "$SCRIPT_DIR/99-dcc-usb-connector.rules" /etc/udev/rules.d/
+sudo udevadm control --reload-rules
+sudo udevadm trigger --subsystem-match=tty
+echo -e "${GREEN}✓ Udev rule installed${NC}"
+echo
+
+# Install systemd user service
+echo "Installing systemd user service..."
+mkdir -p ~/.config/systemd/user/
+cp "$SCRIPT_DIR/dcc-usb-connector.service" ~/.config/systemd/user/
+systemctl --user daemon-reload
+echo -e "${GREEN}✓ Systemd service installed${NC}"
+echo
+
+# Enable lingering (allows user services to run without being logged in)
+echo "Enabling systemd lingering for user..."
+if loginctl show-user "$USER" | grep -q "Linger=yes"; then
+    echo -e "${GREEN}✓ Lingering already enabled${NC}"
+else
+    sudo loginctl enable-linger "$USER"
+    echo -e "${GREEN}✓ Lingering enabled${NC}"
+fi
+echo
+
+# Check user groups
+echo "Checking user permissions..."
+if groups "$USER" | grep -q '\bdialout\b'; then
+    echo -e "${GREEN}✓ User is in 'dialout' group${NC}"
+else
+    echo -e "${YELLOW}Warning: User is not in 'dialout' group${NC}"
+    echo "You may need to add yourself to the dialout group:"
+    echo "  sudo usermod -a -G dialout $USER"
+    echo "Then log out and log back in for changes to take effect."
+fi
+echo
+
+# Check for ncat
+echo "Checking for required tools..."
+if command -v ncat &> /dev/null; then
+    echo -e "${GREEN}✓ ncat is installed${NC}"
+else
+    echo -e "${YELLOW}Warning: ncat is not installed${NC}"
+    echo "Install it with: sudo dnf install nmap-ncat"
+fi
+echo
+
+# Summary
+echo "=========================================================="
+echo -e "${GREEN}Installation complete!${NC}"
+echo
+echo "The service will automatically start when USB device 1a86:7523"
+echo "is connected to /dev/ttyUSB0"
+echo
+echo "To test:"
+echo "  1. Plug in the USB device"
+echo "  2. Check service status: systemctl --user status dcc-usb-connector.service"
+echo "  3. Test connection: telnet localhost 2560"
+echo
+echo "To manually control:"
+echo "  Start:  systemctl --user start dcc-usb-connector.service"
+echo "  Stop:   systemctl --user stop dcc-usb-connector.service"
+echo "  Status: systemctl --user status dcc-usb-connector.service"
+echo
+echo "To view logs:"
+echo "  journalctl --user -u dcc-usb-connector.service -f"
+echo
+echo "To uninstall:"
+echo "  sudo rm /etc/udev/rules.d/99-dcc-usb-connector.rules"
+echo "  rm ~/.config/systemd/user/dcc-usb-connector.service"
+echo "  systemctl --user daemon-reload"
+echo "  sudo udevadm control --reload-rules"
+echo

connector/test-udev-autostart.sh

@@ -0,0 +1,147 @@
+#!/usr/bin/env bash
+#
+# Test script for DCC USB-to-Network Bridge auto-start/stop functionality
+#
+# This script helps verify that the service starts when the USB device
+# is connected and stops when it's removed.
+#
+# Usage:
+#   ./test-udev-autostart.sh
+#
+
+set -e
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+NC='\033[0m' # No Color
+
+echo -e "${BLUE}=== DCC USB-to-Network Bridge Auto-Start/Stop Test ===${NC}"
+echo
+
+# Check if udev rule is installed
+echo -e "${BLUE}1. Checking udev rule installation...${NC}"
+if [ -f /etc/udev/rules.d/99-dcc-usb-connector.rules ]; then
+    echo -e "${GREEN}✓ Udev rule is installed${NC}"
+    echo "   Location: /etc/udev/rules.d/99-dcc-usb-connector.rules"
+else
+    echo -e "${RED}✗ Udev rule is NOT installed${NC}"
+    echo "   Run: sudo cp 99-dcc-usb-connector.rules /etc/udev/rules.d/"
+    exit 1
+fi
+echo
+
+# Check if service is installed
+echo -e "${BLUE}2. Checking systemd service installation...${NC}"
+if [ -f ~/.config/systemd/user/dcc-usb-connector.service ]; then
+    echo -e "${GREEN}✓ Systemd service is installed${NC}"
+    echo "   Location: ~/.config/systemd/user/dcc-usb-connector.service"
+else
+    echo -e "${RED}✗ Systemd service is NOT installed${NC}"
+    echo "   Run: cp dcc-usb-connector.service ~/.config/systemd/user/"
+    exit 1
+fi
+echo
+
+# Check lingering
+echo -e "${BLUE}3. Checking systemd lingering...${NC}"
+if loginctl show-user "$USER" | grep -q "Linger=yes"; then
+    echo -e "${GREEN}✓ Lingering is enabled${NC}"
+else
+    echo -e "${YELLOW}⚠ Lingering is NOT enabled${NC}"
+    echo "   Services may not start automatically when you're not logged in"
+    echo "   Run: sudo loginctl enable-linger $USER"
+fi
+echo
+
+# Check if device is connected
+echo -e "${BLUE}4. Checking USB device...${NC}"
+if lsusb | grep -q "1a86:7523"; then
+    echo -e "${GREEN}✓ USB device 1a86:7523 is connected${NC}"
+    lsusb | grep "1a86:7523"
+    
+    if [ -e /dev/ttyUSB0 ]; then
+        echo -e "${GREEN}✓ /dev/ttyUSB0 exists${NC}"
+        ls -l /dev/ttyUSB0
+    else
+        echo -e "${YELLOW}⚠ /dev/ttyUSB0 does NOT exist${NC}"
+        echo "   The device may be on a different port"
+        echo "   Available ttyUSB devices:"
+        ls -l /dev/ttyUSB* 2>/dev/null || echo "   (none found)"
+    fi
+else
+    echo -e "${YELLOW}⚠ USB device 1a86:7523 is NOT connected${NC}"
+    echo "   Please plug in the device to test"
+fi
+echo
+
+# Check service status
+echo -e "${BLUE}5. Checking service status...${NC}"
+if systemctl --user is-active --quiet dcc-usb-connector.service; then
+    echo -e "${GREEN}✓ Service is RUNNING${NC}"
+    systemctl --user status dcc-usb-connector.service --no-pager -l
+else
+    echo -e "${YELLOW}⚠ Service is NOT running${NC}"
+    echo "   Status:"
+    systemctl --user status dcc-usb-connector.service --no-pager -l || true
+fi
+echo
+
+# Test udev rule
+echo -e "${BLUE}6. Testing udev rule (if device is connected)...${NC}"
+if [ -e /dev/ttyUSB0 ]; then
+    echo "   Running: udevadm test /sys/class/tty/ttyUSB0"
+    echo "   Looking for SYSTEMD_USER_WANTS..."
+    if udevadm test /sys/class/tty/ttyUSB0 2>&1 | grep -q "SYSTEMD_USER_WANTS"; then
+        echo -e "${GREEN}✓ Udev rule is triggering systemd${NC}"
+        udevadm test /sys/class/tty/ttyUSB0 2>&1 | grep "SYSTEMD_USER_WANTS"
+    else
+        echo -e "${RED}✗ Udev rule is NOT triggering systemd${NC}"
+        echo "   The rule may not be matching correctly"
+    fi
+else
+    echo -e "${YELLOW}⚠ Cannot test udev rule - device not connected${NC}"
+fi
+echo
+
+# Check network port
+echo -e "${BLUE}7. Checking network port 2560...${NC}"
+if netstat -tuln 2>/dev/null | grep -q ":2560" || ss -tuln 2>/dev/null | grep -q ":2560"; then
+    echo -e "${GREEN}✓ Port 2560 is listening${NC}"
+    netstat -tuln 2>/dev/null | grep ":2560" || ss -tuln 2>/dev/null | grep ":2560"
+else
+    echo -e "${YELLOW}⚠ Port 2560 is NOT listening${NC}"
+    echo "   Service may not be running or ncat failed to start"
+fi
+echo
+
+# Summary and instructions
+echo -e "${BLUE}=== Test Summary ===${NC}"
+echo
+echo "To test auto-start/stop behavior:"
+echo
+echo "1. ${YELLOW}Monitor the service in one terminal:${NC}"
+echo "   watch -n 1 'systemctl --user status dcc-usb-connector.service'"
+echo
+echo "2. ${YELLOW}Monitor udev events in another terminal:${NC}"
+echo "   udevadm monitor --property --subsystem-match=tty"
+echo
+echo "3. ${YELLOW}Plug in the USB device${NC} and watch:"
+echo "   - Udev should detect the device"
+echo "   - Service should automatically start"
+echo "   - Port 2560 should become available"
+echo
+echo "4. ${YELLOW}Unplug the USB device${NC} and watch:"
+echo "   - Udev should detect device removal"
+echo "   - Service should automatically stop (thanks to StopWhenUnneeded=yes)"
+echo "   - Port 2560 should close"
+echo
+echo "5. ${YELLOW}Check logs:${NC}"
+echo "   journalctl --user -u dcc-usb-connector.service -f"
+echo
+echo "Expected behavior:"
+echo "  • Device connected  → Service starts → Port 2560 opens"
+echo "  • Device removed    → Service stops  → Port 2560 closes"
+echo