HTTP vs MQTT for IoT Power Monitoring¶
Why BuckPow uses HTTP instead of MQTT for device communication.
The Question¶
When building an IoT power monitor, should you use HTTP or MQTT for sending measurements to the server?
Short Answer¶
HTTP for BuckPow. Here's why.
MQTT: What It Does Well¶
MQTT is a lightweight publish-subscribe protocol designed for constrained devices:
- Low overhead — 2-byte fixed header
- Persistent connection — No TCP handshake per message
- QoS levels — Guaranteed delivery (0, 1, 2)
- Retained messages — Last value available on subscribe
- Wildcard topics — Hierarchical subscriptions
When MQTT Shines¶
- Thousands of devices publishing simultaneously
- Unreliable networks with frequent disconnects
- Real-time dashboards requiring sub-second latency
- Bidirectional control (device ← server)
Why BuckPow Chose HTTP¶
1. Simplicity¶
HTTP is universal. Every language, every platform, every device has an HTTP client.
// ESP32 HTTP — no special library needed
HTTPClient http;
http.begin(url);
http.addHeader("Content-Type", "application/json");
int code = http.POST(payload);
MQTT requires:
- A broker (Mosquitto, EMQX, HiveMQ)
- Client library (PubSubClient, AsyncMqttClient)
- Topic management
- Connection lifecycle handling
2. No Broker Dependency¶
HTTP is point-to-point. Device talks directly to server.
MQTT requires a broker running 24/7:
HTTP:
One less thing to deploy, configure, and monitor.
3. Standard Authentication¶
HTTP uses standard Authorization headers:
MQTT authentication is broker-specific and varies by implementation.
4. RESTful API Design¶
HTTP maps naturally to REST:
| Operation | HTTP Method |
|---|---|
| Send measurement | POST /api/v1/measurements |
| Get measurements | GET /api/v1/measurements |
| Export data | GET /api/v1/measurements/export/csv |
MQTT is topic-based, not resource-based. You lose REST semantics.
5. Firewall Friendly¶
HTTP (port 80/443) passes through corporate firewalls, proxies, and load balancers.
MQTT (port 1883/8883) often requires firewall rules and special configuration.
6. Device Auto-Registration¶
BuckPow auto-registers unknown devices on first POST:
POST /api/v1/measurements
{
"device_id": "esp32-01",
"bus_voltage": 5.12,
"current": 241,
"power": 1234
}
No pre-configuration needed. The device just works.
The Trade-offs¶
What You Lose with HTTP¶
| MQTT Feature | HTTP Equivalent |
|---|---|
| Persistent connection | New TCP connection per request |
| QoS guarantees | Application-level retry |
| Bidirectional push | Polling or WebSocket |
| Wildcard subscriptions | REST queries with filters |
What BuckPow Gains¶
| Benefit | Impact |
|---|---|
| No broker | Simpler deployment |
| Standard auth | Easier integration |
| REST semantics | Clear API design |
| Universal support | Any device can connect |
BuckPow's Retry Strategy¶
Since HTTP has no built-in QoS, BuckPow implements retry with backoff:
// Firmware retry logic
if (millis() - lastApiFail < RETRY_MS) return; // 10s backoff
int code = http.POST(payload);
if (code == 201) {
// Success
} else {
lastApiFail = millis(); // Start backoff
}
Server-side rate limiting prevents abuse:
When MQTT Would Be Better¶
BuckPow's HTTP approach works well for:
- Small to medium deployments (< 100 devices)
- Local network monitoring
- Experiment-based workflows
Consider MQTT if you need:
- Real-time bidirectional control
- Thousands of devices publishing simultaneously
- Ultra-low latency (< 100ms)
- Aggressive power saving (persistent connection)
Future: MQTT Support¶
BuckCow may add MQTT as an optional ingestion endpoint:
This would allow MQTT-native devices to participate alongside HTTP devices.
Conclusion¶
HTTP is the right choice for BuckPow's use case:
- Simple — No broker, no extra dependencies
- Universal — Works with any device, any language
- RESTful — Clean API design
- Battle-tested — Decades of tooling and support
MQTT is excellent for other scenarios. For a self-hosted energy observability platform, HTTP wins on simplicity.