IoT Communication Solutions

Light Weight UDP Message Queue Protocol — XEUPD

Protocol v1.1 · May 2026

MQTT over UDP combines MQTT semantics (topics, payloads, publish/subscribe) with UDP's low overhead and a custom application-level reliability layer — ACK/NAK, retry, fragmentation, and reassembly. Purpose-built for IoT telemetry, industrial automation, and constrained devices with limited memory and CPU.

Ultra-Low Latency

Removes TCP connection overhead entirely — ultra-fast delivery for time-critical IoT telemetry and industrial control where every millisecond counts.

Custom Reliability

Application-level ACK/NAK, retry, and fragmentation/reassembly — delivery guarantees without TCP's heavy connection state and handshake overhead.

Constrained Devices

Compact 30-byte binary header with minimal memory and CPU footprint — ideal for embedded MCUs, low-power sensor nodes, and edge gateways.

Protocol features

Ultra-low latency over connectionless UDP

Custom ACK / NAK reliability layer

Intelligent fragmentation & reassembly

QoS 0 / 1 / 2 messaging modes

HMAC-SHA256 authentication & DTLS support

30-byte binary packet header — EUI-64 device ID

Sliding window retry (4–7 segments recommended)

Session recovery & duplicate detection

System Architecture

Client · Broker · Subscribers

Clients construct MQTT-style payloads, fragment them into UDP segments, and transmit with an application-level reliability layer. The broker validates, buffers, and reassembles before dispatching to subscribers.

IoT Client

—Payload Builder
—Fragmentation Engine
—Reliable UDP Sender
—ACK / Retry Handler (QoS 0/1/2)
—HMAC-SHA256 Authentication

UDP Broker

—UDP Listener (Port 1774)
—Packet Validator + CRC Check
—Reassembly Engine
—Message Dispatcher
—Auth + Signature Verification

Subscribers

—Sensor / Edge Applications
—Real-time Dashboards
—Cloud MQTT Bridge
—Alert & Notification Systems
—Data Logging Pipelines

Fig 1 — MQTT over UDP System Architecture (Protocol v1.1)

Packet Format Specification

30-byte header + variable RawData

Each UDP packet consists of a fixed 30-byte binary header followed by variable-length RawData. Minimum packet size is 32 bytes; MTU target is 1472 bytes for standard Ethernet.

Header fields

DeviceID · 8B · uint64 · EUI-64 Signature · 8B · uint64 · HMAC-SHA256 MsgType · 2B · uint16 Timestamp · 4B · uint32 · Unix epoch SegmentNum · 2B · uint16 TotalSegments · 2B · uint16 DataLength · 2B · uint16 CRC · 2B · CRC16-CCITT RawData · Variable bytes

RawData payload format

[ TopicLen: 2B ] → [ Topic: UTF-8 string ] → [ PayloadLen: 2B ] → [ PayloadData: UTF-8/Binary ]

Packet constraints & QoS levels

32 B

Min packet (header only)

1472 B

Recommended MTU target

65 KB

Max packet size

0 / 1 / 2

QoS levels supported

Message types

Code	Type	Direction
0x0001	MSG_PUBLISH	Client → Server
0x0002	MSG_SUBSCRIBE	Client → Server
0x0003	MSG_UNSUBSCRIBE	Client → Server
0x0004	MSG_PINGREQ	Client → Server
0x0005	MSG_CONNECT	Client → Server
0x0006	MSG_DISCONNECT	Client → Server

Code	Type	Meaning
0x1001	ACK_SUCCESS	Segment acknowledged
0x1002	ACK_COMPLETE	Full message received
0x2001	NAK_AUTH_FAIL	Auth failure
0x2002	NAK_INVALID_SEG	Bad segment number
0x2003	NAK_CHECKSUM	CRC mismatch
0x2004/5	NAK_MALFORMED/SIG	Invalid packet

Fig 2 — Binary Packet Format with Header Fields, Message Types, and QoS Model

Protocol Comparison

MQTT/TCP · MQTT/UDP · XEUPD

XEUPD bridges the gap between UDP speed and enterprise-grade reliability — addressing every UDP limitation while maintaining the latency advantage over TCP-based MQTT.

Feature	MQTT / TCP	MQTT / UDP	XEUPD
Transport	TCP	UDP	UDP + Reliability Layer
Connection	Stateful (3-way HS)	Connectionless	Session-aware over UDP
Reliability	Built-in	None	Custom ACK + Retry
Latency	Moderate	Very Low	Ultra-Low
Scalability	Medium	Very High	Extremely High
IoT Suitability	Good	Very Good	Excellent
Security	TLS	DTLS / Custom	XEUPD Secure Layer
Best Use Cases	Standard Messaging	Gaming, VoIP	IoT, Medical, Telemetry

Fig 3 — Protocol comparison: MQTT/TCP vs MQTT/UDP vs XEUPD