---
title: "Building W5500 TCP Client with Lua Scripts(Language) — FlexLua Platform"
url: "https://maker.wiznet.io/TheoIm/projects/building-w5500-tcp-client-with-lua-scripts-language--flexlua-platform/"
markdown_url: "https://maker.wiznet.io/TheoIm/projects/building-w5500-tcp-client-with-lua-scripts-language--flexlua-platform/md"
type: "UCC: User Created Content"
author: "FlexLua"
author_url: "https://zhuanlan.zhihu.com/p/696491840"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "FlexLua"
original_url: "https://zhuanlan.zhihu.com/p/696491840"
published: "2025-11-20"
language: "en"
hardware: ["WIZnet W5500"]
likes: 0
views: 398
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# Building W5500 TCP Client with Lua Scripts(Language) — FlexLua Platform

> Use Lua scripts with FlexLua to build a W5500 TCP client quickly. Core APIs handle sockets and errors, so only simple Lua code is needed.

Original author: FlexLua (source: https://zhuanlan.zhihu.com/p/696491840)

## Components

- **WIZnet W5500** x 1 ([docs](https://docs.wiznet.io/Product/Chip/Ethernet/W5500))

WIZnet parts: W5500 ([Datasheet](https://docs.wiznet.io/Product/Chip/Ethernet/W5500/datasheet?utm_source=maker&utm_medium=project&utm_campaign=w5500), [product hub](https://maker.wiznet.io/products/w5500/))

## Article

## 📌 What This Article Covers

This article introduces how to build a **W5500 TCP Client using only Lua scripts** through the **FlexLua platform**.

### Common challenges when developing Ethernet-based IoT devices:

- Socket management, reconnection handling, exception recovery… more code than expected

- Simple tests require full C firmware rebuild every time

- Quick PoC development becomes burden due to complex development environment

**FlexLua** simplifies this by wrapping W5500 control into Lua script APIs. Complex network logic is handled by the Core, and users only need to **write a few lines of Lua code**.

---

## 💡 What is Lua?

**Lua is a lightweight scripting language that runs efficiently even on MCUs.**

### Key Features:

- **Small code size**: Optimized for embedded environments

- **Simple syntax**: Easy to learn for C/Python developers

- **Easy C integration**: Hardware functions can be easily exposed as APIs

- **Instant execution**: Script modification → immediate execution (no compilation needed)

### Why use Lua in embedded systems?

**Traditional C firmware development:**

```plaintext
Code edit → Compile → Flash upload → Test → Edit again → Repeat...
```

**Lua script approach:**

```plaintext
Script edit → Immediate execution → See results → Done
```

**FlexLua** is a platform that **encapsulates W5500 network APIs** on top of this Lua environment.

---

## 🎯 What This Example Does

Using **ShineBlink Core board + W5500 module**, this example creates a basic TCP client that communicates with a server:

**Operation:**

- **W5500 (Client) → Server**: Send 5 bytes every 5 seconds

- **Server → W5500 (Client)**: Send 10 bytes every 1 second

This is a simple demo showing **basic TCP Client communication implemented purely in Lua script**.

---

## 🔧 Core APIs — Only 3 Functions

FlexLua Core simplifies W5500 operation into **three functions**:

| Function | Purpose |
| --- | --- |
| `LIB_EthTcpConfig()` | TCP configuration and initialization (IP, MAC, port, etc.) |
| `LIB_EthTcpRecv()` | Receive data from server |
| `LIB_EthTcpSend()` | Send data to server |

Combining these three functions is all you need to build W5500-based TCP Client functionality.

---

## 🔌 Hardware Connection

![](https://maker.wiznet.io/upload/ckeditor5/825278978%5F1763647541%2Epng)

Connection between ShineBlink Core and W5500:

- **SPI Communication**: MOSI, MISO, SCK, CS

- **Power**: 5V (or 3.3V compatible)

- **Reset Pin**: Optional

This example drives W5500 at **5V**, but **3.3V operation is also supported**.

---

## 📦 W5500 Module Used

![](https://maker.wiznet.io/upload/ckeditor5/825278978%5F1763647555%2Epng)

Standard W5500 Ethernet module features:

- Built-in RJ45 connector

- SPI interface

- 3.3V/5V compatible

---

## 💻 Example Lua Code

This script runs directly in FlexLua and operates the complete W5500 TCP Client functionality:

```plaintext
LIB_UsbConfig("CDC")
LIB_10msTimerConfig("ENABLE")

mac = {0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}
sip = {192, 168, 1, 200}
subm = {255,255,255,0}
gw = {192, 168, 1, 1}
dns = {8,8,8,8}
tip = {192, 168, 1, 103}
s_port = 1234
c_port = 54321
heart_beat = 0

LIB_EthTcpConfig("D4","D5",mac,sip,subm,gw,dns,tip,s_port,c_port,heart_beat)

cnt_10ms = 0
send_tab = {1,2,3,4,5}

function LIB_10msTimerCallback()
    cnt_10ms = cnt_10ms + 1
end

while(GC(1) == true)
do
    recv_flag,recv_tab = LIB_EthTcpRecv()
    if recv_flag == 1 then
        print(string.format("w5500 tcp client receive %d bytes", #recv_tab))
        for k,v in ipairs(recv_tab) do
            print(k,v)
        end
    end

    if cnt_10ms >= 500 then
        cnt_10ms = 0
        LIB_EthTcpSend(send_tab)
    end
end
```

### Code Breakdown:

**Initialization:**

- Configure USB as CDC for debugging output

- Enable 10ms timer for periodic control

**Network Configuration:**

- Set W5500 IP address (192.168.1.200)

- Define server IP (192.168.1.103) and port (1234)

- Configure MAC address and gateway

**Main Loop:**

- Check for received data with `LIB_EthTcpRecv()`

- Send data every 5 seconds (10ms × 500 counts)

- Print received data in real-time

---

## 📡 Actual Operation Results

### Server Side Data Log

![](https://maker.wiznet.io/upload/ckeditor5/825278978%5F1763647624%2Epng)

Server operation:

- Sends **10 bytes to Core** every 1 second

- Receives **5 bytes from Core** every 5 seconds

### Client (Core + W5500) Side Reception

![](https://maker.wiznet.io/upload/ckeditor5/825278978%5F1763647637%2Epng)

Core device receiving from server:

- **10 bytes received** every 1 second

- Real-time data output display

---

## ⭐ Advantages of This Approach

### 🚀 Rapid Prototyping

- Instant testing without C code compilation/upload

- Change behavior by simply editing scripts

### 🎯 Simple API

- Complex socket control logic hidden

- TCP Client implementation with just 3 functions

### 🔧 Easy Maintenance

- Network configuration changes via script editing

- No hardware reprogramming required

### 📚 Gentle Learning Curve

- Accessible even for C/embedded beginners

- Intuitive Lua syntax

---

## 🎓 Application Areas

FlexLua + W5500 combination is suitable for:

- **IoT Sensor Nodes**: Simple data collection and transmission

- **Test Equipment**: Quick network functionality verification

- **Educational Platforms**: Embedded networking learning

- **Prototype Development**: Fast implementation in PoC stage

---

## 💬 Conclusion

This example demonstrates that **W5500 TCP Client functionality can be implemented with very simple scripts** through the FlexLua environment.

**Key Takeaways:**

- ✅ Complex network socket control automatically handled by Core

- ✅ Users implement TCP communication with just a few lines of Lua

- ✅ Instant testing without compilation

- ✅ Dramatically increased development speed for embedded makers

**"You can build network devices with W5500 without C firmware"** — this is the new possibility that FlexLua presents.

---

Source: https://maker.wiznet.io/TheoIm/projects/building-w5500-tcp-client-with-lua-scripts-language--flexlua-platform/