---
title: "STM32 Ethernet with W5500 (PART 7): STM32 as MQTT client"
url: "https://maker.wiznet.io/irina/projects/stm32-ethernet-with-w5500-part-7--stm32-as-mqtt-client/"
markdown_url: "https://maker.wiznet.io/irina/projects/stm32-ethernet-with-w5500-part-7--stm32-as-mqtt-client/md"
type: "UCC: User Created Content"
author: "ControllersTech"
author_url: "https://www.youtube.com/watch?v=Qr-dgzsofiY"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "ControllersTech"
original_url: "https://www.youtube.com/watch?v=Qr-dgzsofiY"
published: "2025-12-18"
language: "en"
likes: 0
views: 708
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---
# STM32 Ethernet with W5500 (PART 7): STM32 as MQTT client
> STM32 with W5500 tutorial shows how to implement an MQTT client over Ether, enabling pub/sub IoT communication and realtime control with hardware TCP/IP support
Original author: ControllersTech (source: https://www.youtube.com/watch?v=Qr-dgzsofiY)
## Documents and links
- [STM32 W5500 MQTT Client](https://controllerstech.com/stm32-w5500-mqtt-client/)
## Article
## 👤AUTHOR
A maker/embedded developer demonstrating how to use the **WIZnet W5500 Ethernet controller** with an **STM32 microcontroller** to implement a **full MQTT client stack**.
The series (PART 7) focuses specifically on **network-level MQTT operations** with publish/subscribe messaging.
🔗 YouTube Video: [https://www.youtube.com/watch?v=Qr-dgzsofiY](https://www.youtube.com/watch?v=Qr-dgzsofiY&utm_source=chatgpt.com)
---
## 🎯PROJECT DESCRIPTION
Created on** December 13, 2025 ~ December 17,2025**
This video shows how to configure an STM32 microcontroller to communicate over Ethernet using the **W5500 hardware TCP/IP controller** and connect to an **MQTT broker**.
The goal is to enable the STM32 to act as a **fully functional MQTT client**, capable of:
- Publishing sensor data to an MQTT topic
- Subscribing to control topics for remote commands
- Handling network connectivity reliably over Ethernet
- Supporting real-time data exchange between embedded device and server/cloud
Unlike simple TCP examples, using MQTT allows efficient publish/subscribe messaging—ideal for IoT and remote monitoring.
---
## 🧩KEY COMPONENTS USED
#### 🧠Hardware
- **STM32 Microcontroller** (any Cortex-M series supporting Ethernet + SPI)
- **WIZnet W5500 Ethernet Controller** – provides hardware TCP/IP stack
- Ethernet PHY + RJ45
- Optional sensors/actuators interfaced with STM32
#### 🔌 Network & Protocol
- Ethernet physical link via W5500
- MQTT protocol (TCP 1883)
- MQTT broker (could be local or cloud, e.g., Mosquitto)
---
## 🧠**SYSTEM OVERVIEW**
```plaintext
[STM32 MCU]
│
SPI │
â–¼
[W5500 Ethernet]
│
Ethernet
│
[MQTT Broker (server/cloud)]
├── Publishes
└── Subscribes
```
Here the **STM32 publishes its sensor states** and **receives commands** using MQTT topics. W5500 handles all **TCP/IP protocol offloading** so the MCU can focus on application logic.
---
## ✔VIDEO LESSONS
#### 🔹 1) W5500 as network interface
The W5500’s hardware TCP/IP stack allows stable Ethernet communication with minimal STM32 overhead.
#### 🔹 2) MQTT Implementation
Implemented as a client that:
- connects to a broker
- subscribes to topics
- publishes data
- handles reconnect logic
This enables real-time IoT control without Wi-Fi or external networking stacks.
MQTT uses a **publish/subscribe** system with three main parts:
1. **Publisher** – The device or program that sends data.
Example: A temperature sensor publishing the current room temperature.
2. **Subscriber** – The device or program that wants to receive data.
Example: A mobile app that shows the temperature reading.
3. **Broker** – The middleman (server) that connects publishers and subscribers.
Example: An MQTT broker like Mosquitto, HiveMQ, or EMQX.
#### 🔹 3) Publish & Subscribe Patterns
Sensor data can be periodically published, and remote commands (e.g., actuators) can be handled via subscribed topics.
---
## 🧪USE CASES
- Embedded IoT monitoring
- Industrial sensor networks
- Real-time control systems
- Remote data logging dashboards
- MQTT-based automation
- Home/Building automation with Ethernet connectivity
---
## 🧠ENGINEERING INSIGHTS
#### 💡 Reliable Networking
Using **W5500’s hardware TCP/IP** drastically simplifies implementing higher-level protocols like MQTT on resource-limited MCUs.
#### 🔌 Offloaded Protocol Stack
The MCU does not run full TCP/IP or network stack—W5500 handles ARP, IP, TCP, UDP—reducing timing issues and memory pressure.
#### 📡 MQTT Efficiency
MQTT’s lightweight publish/subscribe model fits embedded platforms where:
- bandwidth is limited
- connection reliability matters
- multiple endpoints share topics
---
## 📡TUTORIALS AND PROJECTS
[](https://controllerstech.com/stm32-hal/w5500-ethernet-series/#google_vignette)
#### Wiznet Maker site
**STM32 Ethernet with W5500 (PART 2) : **[**https://maker.wiznet.io/sophia/projects/stm32%2Dethernet%2Dwith%2Dw5500%2Dpart%2D2%2D%2Dtcp%2Dserver%2Dreceive%2Decho%2Dcontrol%2Dled%2Dvia%2Dethernet/**](https://maker.wiznet.io/sophia/projects/stm32%2Dethernet%2Dwith%2Dw5500%2Dpart%2D2%2D%2Dtcp%2Dserver%2Dreceive%2Decho%2Dcontrol%2Dled%2Dvia%2Dethernet/)
**STM32 Ethernet with W5500 (PART 5): **[**https://maker.wiznet.io/bruno/projects/stm32%2Dethernet%2Dwith%2Dw5500%2Dpart%2D5%2D%2Dstm32%2Das%2Dhttp%2Dwebserver%2Dled%2Dcontrol/**](https://maker.wiznet.io/bruno/projects/stm32%2Dethernet%2Dwith%2Dw5500%2Dpart%2D5%2D%2Dstm32%2Das%2Dhttp%2Dwebserver%2Dled%2Dcontrol/)
---
Source: https://maker.wiznet.io/irina/projects/stm32-ethernet-with-w5500-part-7--stm32-as-mqtt-client/