A comprehensive collection of dual-protocol HTTP/TCP servers for transmitting FLEX paging messages via different hardware platforms and integration methods.
This repository provides multiple implementations of FLEX paging servers, each optimized for specific hardware platforms and use cases. All implementations support both HTTP REST API and legacy TCP protocols for maximum compatibility with existing systems and modern cloud integrations.
FLEX (FLexible EXchange) is a digital paging protocol developed by Motorola that operates in the VHF and UHF bands, commonly used for numeric and alphanumeric paging services.
Advanced software-defined radio implementation
A full-featured FLEX paging server for HackRF devices with enterprise-grade features:
- Hardware: HackRF One and compatible SDR devices
- Protocols: HTTP JSON API + legacy TCP serial protocol
- Security: HTTP Basic Authentication with htpasswd compatibility
- Features: Emergency Message Resynchronization (EMR), comprehensive verbose logging, debug mode
- Integration: AWS Lambda compatible response codes, systemd service support
- Use Case: High-performance, production-ready paging infrastructure
Cost-effective ESP32-based implementation
A lightweight FLEX paging server for TTGO ESP32 + SX127x modules:
- Hardware: TTGO LoRa32 V1/V2, TTGO T-Beam, TTGO LoRa32-OLED with ttgo-fsk-tx firmware
- Protocols: HTTP JSON API + legacy TCP protocol
- Features: Direct ESP32 communication, multiple ISM bands support (433/868/915 MHz)
- Dependencies: Requires ttgo-fsk-tx firmware
- Use Case: Portable, low-cost paging solutions, IoT integration
Modern AT command-based implementation
An AT command-based FLEX paging server for broader hardware compatibility:
- Hardware: TTGO LoRa32-OLED, Heltec WiFi LoRa 32 V3, Heltec LoRa32 V3 with flex-fsk-tx firmware
- Protocols: HTTP JSON API + legacy TCP protocol
- Features: Standard AT command interface, universal device compatibility
- Dependencies: Requires flex-fsk-tx firmware
- Use Case: Modern implementation with broader hardware support
Universal monitoring system integration bridge
A webhook service that bridges Grafana Alertmanager to any FLEX paging HTTP server:
- Integration: Grafana Alertmanager → HackRF/TTGO FLEX paging servers
- Compatibility: Works with both HackRF and TTGO HTTP implementations
- Features: HTTPS support, configurable routing, comprehensive logging
- Deployment: Python-based service with systemd support
- Use Case: Automated alerting from monitoring systems to pagers via any backend
This project uses the tinyflex library as a submodule. You must clone recursively or initialize submodules manually:
# Option 1: Clone with submodules (recommended)
git clone --recursive https://github.com/geekinsanemx/flex-http-server.git
# Option 2: If already cloned, initialize submodules
git submodule update --init --recursiveFor production/enterprise use with SDR hardware:
cd hackrf_http_server/
make deps && make
./hackrf_http_server --verboseFor cost-effective/portable solutions (original TTGO firmware):
cd ttgo_http_server/
# First flash your TTGO device with ttgo-fsk-tx firmware
make && ./ttgo_http_server --verboseFor modern AT command implementation (broader hardware support):
cd flex_http_server/
# First flash your TTGO/Heltec device with flex-fsk-tx firmware
make && ./flex_http_server --verboseFor Grafana monitoring integration with any backend:
cd webhooks/grafana-webhook/
# Configure to point to either HackRF or TTGO server
sudo ./grafana-webhook.py --generate-config /etc/grafana-webhook/grafana-webhook.cfg
# Works with both http://localhost:16180 (HackRF or TTGO)All HTTP implementations share a consistent API format:
# Send FLEX paging message
curl -X POST http://localhost:16180/ \
-u admin:passw0rd \
-H "Content-Type: application/json" \
-d '{
"capcode": 1122334,
"message": "Hello World",
"frequency": 931937500
}'- HackRF One or compatible SDR device
- Appropriate antenna for target frequency
- USB 3.0 connection recommended
- Linux system (Ubuntu/Debian preferred)
- TTGO LoRa32 V1/V2, TTGO T-Beam, TTGO LoRa32-OLED
- ttgo-fsk-tx firmware (required dependency)
- USB connection for programming and communication
- Compatible antenna for chosen ISM band
- TTGO LoRa32-OLED, Heltec WiFi LoRa 32 V3, Heltec LoRa32 V3
- flex-fsk-tx firmware (required dependency)
- USB connection for programming and communication
- Compatible antenna for chosen ISM band
- Python 3.8+ environment
- Network access to either HackRF or TTGO HTTP server
- Grafana Alertmanager configuration
| Feature | HackRF Server | TTGO Server | FLEX Server | Grafana Webhook |
|---|---|---|---|---|
| HTTP JSON API | ✅ | ✅ | ✅ | ✅ (receives) |
| TCP Serial Protocol | ✅ | ✅ | ✅ | ❌ |
| Authentication | ✅ htpasswd | ✅ htpasswd | ✅ htpasswd | ✅ (to backend) |
| Debug Mode | ✅ | ✅ | ✅ | ✅ |
| Verbose Logging | ✅ | ✅ | ✅ | ✅ |
| Systemd Service | ✅ | ✅ | ✅ | ✅ |
| AWS Lambda Compatible | ✅ | ✅ | ✅ | ✅ |
| EMR Support | ✅ | ✅ | ✅ | via any backend |
| Multi-band Support | ✅ (VHF/UHF) | ✅ (ISM bands) | ✅ (ISM bands) | N/A |
| Hardware Cost | High (SDR) | Low (ESP32) | Low (ESP32) | Software only |
| Communication Protocol | Direct | Custom binary | AT commands | HTTP client |
| Firmware Required | None | ttgo-fsk-tx | flex-fsk-tx | N/A |
| Backend Compatibility | N/A | N/A | N/A | All servers |
All implementations support similar configuration patterns:
# Network Configuration
BIND_ADDRESS=127.0.0.1
HTTP_LISTEN_PORT=16180
SERIAL_LISTEN_PORT=16175
# Authentication
HTTP_AUTH_CREDENTIALS=passwords
# FLEX Protocol
DEFAULT_FREQUENCY=931937500929.6625 MHz - American Messaging
931.9375 MHz - FLEX (default)
931.4375 MHz - Motorola infrastructure
433.500 MHz - Global ISM band
868.000 MHz - Europe ISM band
915.000 MHz - Americas ISM band
import requests
def send_flex_message(server_url, username, password, capcode, message, frequency=None):
payload = {
'capcode': capcode,
'message': message
}
if frequency:
payload['frequency'] = frequency
response = requests.post(
f'{server_url}/',
auth=(username, password),
json=payload,
headers={'Content-Type': 'application/json'}
)
return response.status_code == 200
# Works with HackRF, TTGO, and FLEX servers
send_flex_message('http://localhost:16180', 'admin', 'passw0rd',
1122334, 'Test message', 931937500)# Grafana webhook → Any FLEX HTTP server
Grafana Alert → Webhook Service → HackRF/TTGO/FLEX Server → FLEX Transmission
# Configure webhook to use HackRF server
FLEX_SERVER_URL=http://localhost:16180 # HackRF server
# Or configure webhook to use TTGO server
FLEX_SERVER_URL=http://localhost:16180 # TTGO server (original firmware)
# Or configure webhook to use FLEX server
FLEX_SERVER_URL=http://localhost:16180 # FLEX server (AT commands)
# Manual monitoring integration (works with all)
curl -X POST http://localhost:16180/ \
-u admin:passw0rd \
-H "Content-Type: application/json" \
-d '{"capcode": 911911, "message": "Server down: web01"}'Each implementation has its own build system and dependencies. See individual README files for specific development instructions:
This project is licensed under the MIT License - see the LICENSE file for details.
This work is based on and inspired by several excellent projects in the SDR and paging community:
- tinyflex - A minimal FLEX paging transmitter that provided the foundation for the FLEX protocol implementation across all our servers
- ttgo-fsk-tx - Original firmware for TTGO LoRa32 development boards that enables FSK transmission. This is a required dependency for the TTGO implementation
- flex-fsk-tx - Modern AT command firmware for TTGO and Heltec development boards. This is a required dependency for the FLEX implementation and provides AT command interface for broader hardware compatibility
- ellisgl - For the hackrf_tcp_server contribution via PR #6 to tinyflex, which helped shape the TCP server implementation and influenced our dual-protocol approach
Special thanks to these developers for their work in software-defined radio and paging protocols. The combination of traditional SDR hardware (HackRF), ESP32-based development boards with original firmware (TTGO with ttgo-fsk-tx), modern AT command implementation (TTGO/Heltec with flex-fsk-tx), and cloud integration (Grafana webhooks) provides users with flexible deployment options ranging from high-performance enterprise solutions to cost-effective IoT implementations.
For issues specific to each implementation:
- HackRF Server: Check HackRF troubleshooting guide
- TTGO Server: Verify ttgo-fsk-tx firmware installation
- FLEX Server: Verify flex-fsk-tx firmware installation
- Grafana Webhook: Review webhook configuration - works with all backends
For general repository issues:
- Check the Issues page
- Create a new issue with details about your specific implementation
- Include hardware setup, OS version, and configuration details
This software is intended for educational and experimental purposes. Users are responsible for ensuring compliance with local regulations regarding radio transmissions and paging frequencies. Always operate within legal power limits and obtain proper licensing when required.
- GNU Radio - The premier software toolkit for software radio
- HackRF - Low cost software defined radio platform
- ttgo-fsk-tx - Required firmware for TTGO implementation
- flex-fsk-tx - Required firmware for FLEX implementation
- Universal Hardware Driver (UHD) - Hardware driver for USRP devices