intercept/docs/TROUBLESHOOTING.md

Troubleshooting

Solutions for common issues.

Python / Installation Issues

"ModuleNotFoundError: No module named 'flask'"

Install Python dependencies first:

pip install -r requirements.txt

# Or with python3 explicitly
python3 -m pip install -r requirements.txt

pip install fails for flask or skyfield

On newer Debian/Ubuntu systems, pip may fail with permission errors or dependency conflicts. Use apt instead:

# Install Python packages via apt (recommended for Debian/Ubuntu)
sudo apt install python3-flask python3-requests python3-serial python3-skyfield

# Then create venv with system packages
python3 -m venv --system-site-packages venv
source venv/bin/activate
sudo venv/bin/python intercept.py

"error: externally-managed-environment" (pip blocked)

This is PEP 668 protection on Ubuntu 23.04+, Debian 12+, and similar systems. Solutions:

# Option 1: Use apt packages (recommended)
sudo apt install python3-flask python3-requests python3-serial python3-skyfield
python3 -m venv --system-site-packages venv
source venv/bin/activate

# Option 2: Use pipx for isolated install
pipx install flask

# Option 3: Force pip (not recommended)
pip install --break-system-packages flask

"TypeError: 'type' object is not subscriptable"

This error occurs on Python 3.7 or 3.8. INTERCEPT requires Python 3.9 or later.

# Check your Python version
python3 --version

# Ubuntu/Debian - install newer Python
sudo apt update
sudo apt install python3.11 python3.11-venv python3-pip

# Run with newer Python
python3.11 -m venv venv
source venv/bin/activate
pip install -r requirements.txt
sudo venv/bin/python intercept.py

Alternative: Use the setup script

The setup script handles all installation automatically, including apt packages:

chmod +x setup.sh
./setup.sh

"pip: command not found"

# Ubuntu/Debian
sudo apt install python3-pip

# macOS
python3 -m ensurepip --upgrade

Permission denied during pip install

# Install to user directory
pip install --user -r requirements.txt

SDR Hardware Issues

No SDR devices found

1. Ensure your SDR device is plugged in
2. Check detection:
   • RTL-SDR: rtl_test
   • LimeSDR/HackRF: SoapySDRUtil --find
3. On Linux, add udev rules (see below)
4. Blacklist conflicting drivers:

   echo "blacklist dvb_usb_rtl28xxu" | sudo tee /etc/modprobe.d/blacklist-rtl.conf
   sudo modprobe -r dvb_usb_rtl28xxu
   

Linux udev rules for RTL-SDR

sudo bash -c 'cat > /etc/udev/rules.d/20-rtlsdr.rules << EOF
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", MODE="0666"
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2832", MODE="0666"
EOF'

sudo udevadm control --reload-rules
sudo udevadm trigger

Then unplug and replug your RTL-SDR.

Device busy error

1. Click "Kill All Processes" in the UI
2. Unplug and replug the SDR device
3. Check for other applications: lsof | grep rtl

LimeSDR/HackRF not detected

Ensure the correct SoapySDR module for your hardware is installed first

1. Verify SoapySDR is installed: SoapySDRUtil --info
2. Check driver is loaded: SoapySDRUtil --find
3. May need udev rules or run as root

Using HackRF/Airspy/LimeSDR with ADS-B

For non-RTL-SDR devices, ADS-B requires readsb compiled with SoapySDR support (standard dump1090 won't work).

Option 1: Run readsb separately and connect via Remote mode

1. Start readsb with your device:

   # HackRF
   readsb --device-type soapysdr --device driver=hackrf --net --quiet
   
   # Airspy
   readsb --device-type soapysdr --device driver=airspy --net --quiet
   
   # LimeSDR
   readsb --device-type soapysdr --device driver=lime --net --quiet
   

2. In Intercept's ADS-B dashboard:

   • Check the "Remote" checkbox
   • Enter Host: localhost and Port: 30003
   • Click START

3. Intercept will connect to readsb's SBS output on port 30003

Option 2: Install readsb with SoapySDR support

On Debian/Ubuntu:

# Install dependencies
sudo apt install build-essential debhelper librtlsdr-dev pkg-config \
    libncurses5-dev libbladerf-dev libhackrf-dev liblimesuite-dev libsoapysdr-dev

# Clone and build
git clone https://github.com/wiedehopf/readsb.git
cd readsb
dpkg-buildpackage -b --no-sign
sudo dpkg -i ../readsb_*.deb

Using HackRF/Airspy with Listening Post

The Listening Post requires rx_fm from SoapySDR utilities for non-RTL-SDR devices.

# Install SoapySDR utilities (includes rx_fm)
sudo apt install soapysdr-tools

# Verify rx_fm is available
which rx_fm

If rx_fm is installed, select your device from the SDR dropdown in the Listening Post - HackRF, Airspy, LimeSDR, and SDRPlay are all supported.

Setting up Icecast for Listening Post Audio

The Listening Post uses Icecast for low-latency audio streaming (2-10 second latency). Intercept will automatically start Icecast when you begin listening, but you must install and configure it first.

Install Icecast:

# Ubuntu/Debian
sudo apt install icecast2

# macOS
brew install icecast

Configure Icecast:

During installation on Debian/Ubuntu, you'll be prompted to configure. Otherwise, edit /etc/icecast2/icecast.xml:

<icecast>
    <authentication>
        <!-- Source password - used by ffmpeg to send audio -->
        <source-password>hackme</source-password>
        <!-- Admin password for web interface -->
        <admin-password>your-admin-password</admin-password>
    </authentication>
    <hostname>localhost</hostname>
    <listen-socket>
        <port>8000</port>
    </listen-socket>
</icecast>

Start Icecast:

# Ubuntu/Debian (as service)
sudo systemctl enable icecast2
sudo systemctl start icecast2

# Or run directly
icecast -c /etc/icecast2/icecast.xml

# macOS
brew services start icecast
# Or: icecast -c /usr/local/etc/icecast.xml

Verify Icecast is running:

• Open http://localhost:8000 in your browser
• You should see the Icecast status page

Configure Intercept (optional):

The default configuration expects Icecast on 127.0.0.1:8000 with source password hackme and mount point /listen.mp3. To change these, modify the scanner config in your API calls or update the defaults in routes/listening_post.py:

scanner_config = {
    # ... other settings ...
    'icecast_host': '127.0.0.1',
    'icecast_port': 8000,
    'icecast_mount': '/listen.mp3',
    'icecast_source_password': 'hackme',
}

Troubleshooting Icecast:

• "Connection refused" errors: Ensure Icecast is running on the configured port
• "Authentication failed": Check the source password matches between Icecast config and Intercept
• No audio playing: Check Icecast status page (http://localhost:8000) to verify the mount point is active
• High latency: Ensure nginx/reverse proxy isn't buffering - add proxy_buffering off; to nginx config

Audio Streaming Issues - Detailed Debugging

If the Listening Post shows "Icecast mount not active" errors or audio doesn't play:

1. Check the console output for errors

Intercept now logs detailed error output. Look for lines starting with [AUDIO]:

[AUDIO] SDR errors: ...     # Problems with rtl_fm/rx_fm (SDR not connected, device busy)
[AUDIO] FFmpeg errors: ...  # Problems with ffmpeg (wrong password, codec issues)

2. Verify SDR is connected and working

# For RTL-SDR
rtl_test -t

# You should see: "Found 1 device(s)"
# If not, check USB connection and drivers

3. Check Icecast password (macOS Homebrew)

On macOS with Homebrew, the Icecast config is at /opt/homebrew/etc/icecast.xml. Check the source password:

grep source-password /opt/homebrew/etc/icecast.xml

If it's different from hackme, update it in the Listening Post Icecast config panel, or change the Icecast config and restart:

brew services restart icecast

4. Verify ffmpeg has required codecs

# Check MP3 encoder is available
ffmpeg -encoders 2>/dev/null | grep mp3

# Should show: libmp3lame
# If not, reinstall ffmpeg with all codecs:
# macOS: brew reinstall ffmpeg
# Linux: sudo apt install ffmpeg

5. Test the pipeline manually

Try running the audio pipeline directly to see errors:

# Test rtl_fm (should produce raw audio data)
rtl_fm -M am -f 118000000 -s 24000 -r 24000 -g 40 2>&1 | head -c 1000 | xxd | head

# Test ffmpeg to Icecast (replace PASSWORD with your source password)
rtl_fm -M am -f 118000000 -s 24000 -r 24000 -g 40 2>/dev/null | \
  ffmpeg -f s16le -ar 24000 -ac 1 -i pipe:0 -c:a libmp3lame -b:a 64k \
  -f mp3 -content_type audio/mpeg icecast://source:PASSWORD@127.0.0.1:8000/listen.mp3

6. Common error messages and solutions

Error	Cause	Solution
No supported devices found	SDR not connected	Plug in SDR, check USB
Device or resource busy	Another process using SDR	Click "Kill All Processes"
401 Unauthorized	Wrong Icecast password	Check password in Icecast config
Connection refused	Icecast not running	Start Icecast service
Encoder libmp3lame not found	ffmpeg missing codec	Reinstall ffmpeg with codecs

WiFi Issues

Monitor mode fails

1. Ensure running as root/sudo
2. Check adapter supports monitor mode: iw list | grep monitor
3. Kill interfering processes: airmon-ng check kill

Permission denied when scanning

Run INTERCEPT with sudo:

sudo -E venv/bin/python intercept.py

Interface not found after enabling monitor mode

Some adapters rename when entering monitor mode (e.g., wlan0 → wlan0mon). The interface should auto-select, but if not, manually select the monitor interface from the dropdown.

Bluetooth Issues

No Bluetooth adapter found

# Check if adapter is detected
hciconfig

# Ubuntu/Debian - install BlueZ
sudo apt install bluez bluetooth

Permission denied

Run with sudo or add your user to the bluetooth group:

sudo usermod -a -G bluetooth $USER

Decoding Issues

No messages appearing (Pager mode)

1. Verify frequency is correct for your area
2. Adjust gain (try 30-40 dB)
3. Check pager services are active in your area
4. Ensure antenna is connected

Cannot install dump1090 in Debian (ADS-B mode)

On newer Debian versions, dump1090 may not be in repositories. The recommended action is to build from source or use the setup.sh script which will do it for you.

No aircraft appearing (ADS-B mode)

1. Verify dump1090 is installed
2. Check antenna is connected (1090 MHz antenna recommended)
3. Ensure clear view of sky
4. Set correct observer location for range calculations or use gpsd

Satellite passes not calculating

1. Ensure skyfield is installed: apt install python3-skyfield
2. Check TLE data is valid and recent
3. Verify observer location is set correctly