A distributed WiFi reconnaissance system using ESP32-S3 nodes and an Orange Pi as coordinator. The goal is passive RF awareness — mapping what is happening in the surrounding WiFi environment without transmitting or interacting with any networks.

Each ESP32 node scans the WiFi environment, builds structured events (not raw data), and ships them over UDP to a coordinator. The coordinator stores events to SQLite. A separate web dashboard reads the database and displays everything in real time via SSE.

The system is designed around a clear separation of concerns: nodes are dumb sensors, the Orange Pi does all storage and analysis, the browser does all rendering. No logic lives on the nodes beyond capturing and formatting events.

Practical use cases this has already demonstrated:

Mapping every network and client device in a city-center apartment building
Detecting sustained deauth flood attacks targeting specific devices (confirmed live)
Reconstructing device travel history from probe request SSID lists
Identifying device types by OUI (phones, IoT devices, laptops, cars, smart home hardware)
Correlating attack victims across multiple impersonated APs using deauth dst MAC

This is a learning/research project covering distributed systems, event-driven architecture, sensor fusion, and detection engineering concepts.

Hardware

Nodes: ESP32-S3 N16R8 (4 active, scattered across apartment)
Coordinator: Orange Pi at 192.168.1.133, runs 24/7 as systemd services
Dev machine: This PC at 192.168.1.101 — coding and flashing only
Flashing: Arduino CLI on this PC

Active nodes

node_id	MAC	Location / Port
F68D6E30	44:1b:f6:8d:6e:30	desk /dev/ttyACM0
A1D658D4	e0:72:a1:d6:58:d4	desk /dev/ttyACM1
A1D700C4	e0:72:a1:d7:00:c4	desk /dev/ttyACM2
A1D6F190	e0:72:a1:d6:f1:90	deployed (another room)

Network

ESP32 nodes connect to: WiFi SSID sandbox
Coordinator IP: 192.168.1.133 (Orange Pi, production)
UDP port: 5005
Dashboard port: 8080

Architecture

[ESP32 nodes] --UDP 5005--> [udp_ingest.py] --write--> [events.db (SQLite)]
                                                               |
[Browser] <--HTTP/SSE 8080-- [dashboard.py] ------read--------+

The two coordinator processes are intentionally separate. The ingestor has one job: receive UDP, write to DB. The dashboard has one job: read DB, serve UI. They communicate only through the database. Each is independently restartable without affecting the other.

Development workflow

All coding is done on this PC. The Orange Pi only runs the deployed files — never edit directly on it.

[This PC] → edit code → rsync → [Orange Pi] → restart services

Sync to Orange Pi

bash /home/sandbox/Documents/projects/esp32_cluster/deploy.sh

This rsyncs coordinator/ to /opt/esp32_cluster/coordinator/ on the Orange Pi, excluding events.db (the Pi keeps its own database).

Restart services after deploy

ssh root@192.168.1.133 'systemctl restart udp_ingest dashboard'

View live logs on Orange Pi

# Ingestor (UDP events coming in)
ssh root@192.168.1.133 'journalctl -u udp_ingest -f'

# Dashboard
ssh root@192.168.1.133 'journalctl -u dashboard -f'

Project structure

esp32_cluster/
├── firmware/
│   └── node/
│       ├── node.ino              # ESP32 node firmware
│       └── config.h              # WiFi creds, coordinator IP, scan/probe config
├── coordinator/
│   ├── udp_ingest.py             # UDP listener — receives packets, validates, writes to SQLite
│   ├── dashboard.py              # FastAPI app — reads SQLite, serves UI + SSE stream
│   ├── templates/
│   │   └── dashboard.html        # Dashboard skeleton HTML
│   ├── static/
│   │   ├── dashboard.css         # All dashboard styles
│   │   └── dashboard.js          # All dashboard logic (vanilla JS)
│   ├── oui.txt                   # IEEE OUI database for vendor lookup (39k entries)
│   ├── udp_ingest.service        # systemd service file for ingestor
│   ├── dashboard.service         # systemd service file for dashboard
│   └── events.db                 # SQLite database — on Orange Pi only, not synced
├── deploy.sh                     # rsync script: this PC → Orange Pi
├── starting_plan.md              # Original architecture design doc
└── README.md                     # This file

Firmware

Each node:

Connects to WiFi sandbox
Scans for nearby APs every 15 seconds (active scan, includes hidden SSIDs)
Captures probe request frames passively (promiscuous mode) between scans
Sends a heartbeat packet every 10 seconds (uptime, free heap, WiFi RSSI to router)
Sends beacon, probe, and heartbeat events as UDP JSON packets to the coordinator
node_id is derived from bytes 2–5 of the ESP32's base MAC address

Event formats

Beacon event (AP discovered):

{
  "node_id": "F68D6E30",
  "ts":      12345,
  "type":    "beacon",
  "conf":    "high",
  "imp":     "normal",
  "ssid":    "NetworkName",
  "bssid":   "AA:BB:CC:DD:EE:FF",
  "rssi":    -65,
  "ch":      6,
  "enc":     "WPA2"
}

Probe event (client device searching for a network):

{
  "node_id": "F68D6E30",
  "ts":      12345,
  "type":    "probe",
  "conf":    "high",
  "imp":     "normal",
  "src_mac": "AA:BB:CC:DD:EE:FF",
  "ssid":    "HomeNetwork",
  "rssi":    -55
}

Deauth / Disassoc event (management frame captured in promiscuous mode):

{
  "node_id": "F68D6E30",
  "ts":      12345,
  "type":    "deauth",
  "src":     "AA:BB:CC:DD:EE:FF",
  "dst":     "11:22:33:44:55:66",
  "bssid":   "AA:BB:CC:DD:EE:FF",
  "reason":  7,
  "rssi":    -61
}

type is deauth (0xC0) or disassoc (0xA0)
dst = FF:FF:FF:FF:FF:FF means broadcast deauth — a classic deauth flood signature
reason is the 802.11 reason code (7 = class 3 frame received from non-associated station, common in attack tools)
Captured passively in the same promiscuous callback as probe requests, flushed to coordinator after each scan cycle

Heartbeat event (node health, sent every 10 seconds):

{
  "node_id":   "F68D6E30",
  "ts":        12345,
  "type":      "heartbeat",
  "uptime_ms": 123456,
  "free_heap": 245000,
  "wifi_rssi": -62
}

imp: high if RSSI >= -50, low if <= -80, else normal
ssid in probe events is the network the device is searching for — empty means wildcard (any network)
Probe dedup: same MAC+SSID suppressed for 30 seconds to avoid flooding
wifi_rssi in heartbeat is the node's own signal to the sandbox AP (not a scanned network)
A node is considered online if a heartbeat arrived within the last 30 seconds; falls back to beacon within 60 seconds if no heartbeat has been received yet

Flashing a node

Requirements: Arduino CLI v1.4.1, ESP32 core v3.3.7, FQBN esp32:esp32:esp32s3, user in dialout group.

# Compile
arduino-cli compile --fqbn esp32:esp32:esp32s3 /home/sandbox/Documents/projects/esp32_cluster/firmware/node/

# Flash — adjust port as needed (check with: ls /dev/ttyACM*)
arduino-cli upload --fqbn esp32:esp32:esp32s3 --port /dev/ttyACM0 \
  /home/sandbox/Documents/projects/esp32_cluster/firmware/node/

The same binary works on every node — node_id is auto-derived from the MAC, no per-node config needed.

Check group membership with groups. You should see dialout.

config.h reference

Constant	Default	Purpose
`WIFI_SSID`	`sandbox`	WiFi network to connect to
`COORDINATOR_IP`	`192.168.1.133`	Orange Pi address
`COORDINATOR_PORT`	`5005`	UDP port
`SCAN_INTERVAL_MS`	`15000`	How often to run a beacon scan (ms)
`PROBE_SNIFF`	`1`	Enable/disable probe sniffing (1/0)
`PROBE_DEDUP_SECS`	`30`	Suppress duplicate probe MAC+SSID (secs)
`PROBE_QUEUE_SIZE`	`32`	Max probe events buffered between scans
`DEAUTH_QUEUE_SIZE`	`32`	Max deauth/disassoc events buffered

Orange Pi — running services

Services are managed by systemd and start automatically on boot.

# Status
ssh root@192.168.1.133 'systemctl status udp_ingest dashboard'

# Restart both
ssh root@192.168.1.133 'systemctl restart udp_ingest dashboard'

# Stop
ssh root@192.168.1.133 'systemctl stop udp_ingest dashboard'

Service files are in coordinator/ and deployed to /etc/systemd/system/ on the Orange Pi. The coordinator files live at /opt/esp32_cluster/coordinator/ on the Orange Pi.

Dashboard

Open http://192.168.1.133:8080 in your browser.

Views

Feed — live beacon event stream across all nodes, capped at 100 rows, newest on top
Networks — deduplicated AP table (by BSSID): times seen, best/avg RSSI, channel, encryption, node count. Sortable by any column. Each row has a ▶ button to open the RSSI history chart for that network.
RSSI history chart — opens from any Networks row. Shows signal strength over time per node (1h / 2h / 6h / 24h selectable). Each node gets its own coloured line. Useful for spotting interference patterns, seeing how signal fluctuates by time of day, and comparing which node consistently hears a given AP better. Updates live as new scans arrive.
Cross-node — side-by-side per-node RSSI for every AP. Shows which node is physically closer to each network. Filter to multi-node only to focus on confirmed cross-node observations.
Clients — probe request data: unique MACs, vendor (OUI lookup), what SSIDs they're searching for, signal, which nodes saw them.
Alerts — deauth/disassoc frame detection with four sections:
- 1h Summary strip — total frames, deauth vs disassoc counts, unique BSSIDs and sources in the last hour
- Most Impersonated Networks — APs whose BSSID is being spoofed as the deauth source, ranked by frame count
- Most Targeted Devices — actual victim devices (by dst MAC), ranked by frames received across all impersonated APs
- Detected Bursts — fires when ≥10 frames for the same BSSID within 5 minutes. Highlighted red when confirmed by 2+ nodes. Reason code 2 at volume is the primary attack indicator.
- Raw Feed — last 100 deauth/disassoc events with full src/dst/BSSID/reason/RSSI detail.
Search — cross-table lookup by any identifier. Supports MAC address, SSID, BSSID, and vendor name (e.g. "Raspberry", "Tuya", "Intel"). Returns all matching data across beacon, probe, and deauth tables in labelled sections. Vendor name search works by matching against the OUI database and finding all devices with those MAC prefixes.
Presence — three sections driven entirely by probe data:
- Present Now — real (non-randomized) MACs seen 2+ times in the last hour. Filters out the city-center noise of transient devices.
- New Arrivals — devices and networks first seen in the last 24 hours, split into two side-by-side tables.
- Regulars — devices and networks seen on 2 or more distinct calendar days. Takes at least two days of data to populate.
Node detail — click a node in the sidebar for stats: total events, unique SSIDs/BSSIDs, RSSI range, first/last seen, uptime, free heap, AP signal, last 100 events.

Node detail

Click any node in the sidebar to open the detail view. Ten stat cards arranged in a 2×5 grid show: status, total events, unique SSIDs, unique BSSIDs, avg RSSI, first seen, last seen, uptime, free heap, and AP signal. Below the cards is a table of the last 100 events for that node.

Sidebar

Always visible: node list with online/offline status dot, last seen time, event count, and a compact heartbeat line (uptime · free heap · AP signal). Nodes are sorted alphabetically by node ID so the order stays fixed as more nodes are added. A node is considered online if a heartbeat was received within the last 30 seconds. Falls back to beacon timestamp (60s threshold) if no heartbeat has been received yet.

UI

Font: Roboto (Google Fonts). Chosen for readability at small sizes — the previous monospace font felt too thin at the smaller label sizes used throughout the dashboard.

Live updates

SSE stream pushes new beacon events as they arrive. The feed updates immediately. All other views (sidebar, networks, chart, cross-node, presence, alerts) refresh on a 2-second debounce so a single scan burst doesn't flood the server with requests.

Observations and notes

Hidden networks

Networks with a blank SSID but valid BSSID, signal, and channel are hidden networks — APs configured not to broadcast their name. They are not hidden from passive scanners. The encryption showing as OPEN is a firmware parsing artifact; the network itself may be encrypted. The BSSID OUI still identifies the manufacturer.

Probe requests and MAC randomization

Modern phones and laptops (iOS since ~2020, Android since ~2021) randomize their MAC address for probe requests. A randomized MAC has bit 1 of the first byte set — the dashboard detects this and labels it "Randomized MAC" instead of doing a meaningless OUI lookup.

What probe data tells you:

Directed probes (with SSID): the device has connected to that network in the past
Wildcard probes (empty SSID): the device is searching for any available network
Probe data maps client devices, not infrastructure — complementary to beacon scan data

Deauth frame noise vs real attacks

The raw deauth feed in the Alerts tab will fill up constantly — deauth and disassoc frames are a normal part of WiFi operation (devices disconnecting, APs doing band steering, power saving). This is expected and not cause for concern.

The Bursts section is the anomaly detector. A single unique source MAC generating 10+ deauth frames for the same BSSID within 5 minutes is not normal operation — it indicates a deauth flood, the standard precursor to a WPA2 handshake capture attack. The attacker forces connected clients to disconnect, captures the 4-way handshake when they reconnect, and then cracks it offline.

Multi-node confirmation (node_count > 1, highlighted red) significantly raises confidence — it means the source is physically close and strong, not a distant weak signal.

OUI lookup

The oui.txt file is the IEEE public OUI database (39,171 entries as of download). It maps the first 3 bytes of a real MAC to a manufacturer name. Used in the Clients tab. Refresh it occasionally by re-running deploy.sh after downloading a fresh copy from https://standards-oui.ieee.org/oui/oui.txt.

Current status

Arduino CLI installed, ESP32 core configured
Node firmware: beacon scan + probe sniffing
Four ESP32-S3 nodes flashed and running
UDP ingestor (udp_ingest.py) — beacon + probe routing with field validation
Web dashboard: Feed, Networks, Cross-node, Clients, Node detail views
OUI vendor lookup in Clients view
Dashboard split into HTML / CSS / JS (no monolithic file)
Deployed to Orange Pi as systemd services (runs 24/7)
All four nodes sending to Orange Pi, confirmed live
Node heartbeat every 10s — uptime, free heap, AP signal, drives online/offline status
RSSI history chart per network (canvas, per-node coloured lines, 1h/2h/6h/24h range)
Presence tab — Present Now, New Arrivals, Regulars
Deauth/disassoc frame detection — burst detection with multi-node confirmation, Alerts tab
Alerts tab — most impersonated networks, most targeted devices, burst detection, raw feed
Search tab — cross-table lookup by MAC, SSID, BSSID, or vendor name
Node detail view — 2×5 stat cards with animated border, fixed alphabetical sidebar order
Attack session reconstruction — group deauth events into discrete sessions by source/time
Scan interval control from dashboard
DB pruning / retention policy (events.db grows indefinitely)

Python dependencies

fastapi
uvicorn

pip install fastapi uvicorn

Languages

Python 34.8%

JavaScript 28.6%

C++ 14.2%

HTML 11.9%

CSS 8%

Other 2.5%

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ESP32 WiFi Recon Cluster

What this is