## The Problem

GPS IoT trackers don't communicate using traditional HTTP/JSON due to cellular bandwidth limitations and modem efficiency constraints in vehicles. Instead, they transmit **raw TCP socket streams** with binary protocols (Teltonika Codec 8/Extended, GT06/Concox) prone to TCP stream fragmentation and intermittent connectivity.

The system requires a listener engine capable of:
- Handling hundreds of concurrent TCP connections without memory exhaustion
- Correctly framing fragmented binary packets from the byte stream
- Validating checksums (CRC16) and dispatching protocol ACK handshakes in real time
- Preventing socket blocking and slow-client starvation

## The Solution

Engineered a **GPS TCP Listener & Decoder Engine** built on pure **Go** utilizing a high-performance socket architecture:

- **TCP Stream Framing**: custom framing loop extracting packet delimiters and variable length bytes safely.
- **Binary Decoders**: protocol decoders for Teltonika (Codec 8/Extended) and GT06 with strict CRC16 validation.
- **Memory Optimization**: leveraging `sync.Pool` byte buffers to eliminate allocation overhead during heavy telemetry bursts.
- **Pipeline Fan-out**: validated telemetry positions are dispatched via Redis Streams to ingestion workers and persisted into TimescaleDB hypertables.

### Architecture

```
GPS Tracker (TCP) ──> [ net.Listen Go Worker Pool ]
                               │
                      [ Binary Framing & CRC16 ]
                               │
                      [ Decoder (Teltonika / GT06) ]
                               │
               ┌───────────────┴───────────────┐
               ▼                               ▼
    [ Redis Pub/Sub Fan-out ]      [ TimescaleDB Hypertable ]
```

## Results & Implementation Guide

- Capable of decoding thousands of telemetry points per second with sub-millisecond latencies.
- Full architectural breakdown and runnable implementation are documented in the [GPS Backend Series](/en/series/gps-backend-series/).