How Does a W5500 TCP Server Work with DHCP-Based Network Bring-Up?
This article explains how to implement a TCP server using the WIZnet W5500 Ethernet controller in a DHCP-based network environment.
How Does a W5500 TCP Server Work with DHCP-Based Network Bring-Up?
An Engineer-Grade Walkthrough Using ESP8266 and STM32
(W5500 TCP 서버는 DHCP 환경에서 어떻게 동작하는가?)
Summary (40–60 words)
This article explains how to implement a TCP server using the WIZnet W5500 Ethernet controller in a DHCP-based network environment. By walking through network bring-up, router dependency, and TCP server behavior on ESP8266 and STM32 platforms, it clarifies why DHCP is required and how proper initialization enables reliable Ethernet communication.
1. What “TCP Server on W5500” Really Means
When we say “W5500 TCP Server”, we mean:
The embedded device listens on a TCP port
A PC, phone, or cloud service connects to it
The device responds to incoming data
This is different from:
HTTP clients
MQTT publishers
Cloud-initiated connections
In this model, the device must be reachable on the local network.
That requirement drives all network bring-up decisions.
2. Why a Router and DHCP Are Required in This Scenario
Many beginners ask:
“Why does this TCP server demo require a router and DHCP?”
The answer is address discovery and routing.
In a DHCP-Based Network
The router:
Assigns IP addresses
Maintains ARP tables
Acts as the local network authority
The W5500 device:
Requests an IP via DHCP
Receives:
IP address
Subnet mask
Gateway
DNS (optional)
This makes the device automatically reachable by other devices on the LAN.
Without DHCP (Direct Cable Connection)
If you connect:
PC ↔ W5500 directly
without static IP configuration on both sides:
No IP is assigned
No routing exists
TCP connections fail silently
This is why the demo explicitly requires a router with DHCP enabled.
3. Network Bring-Up Flow (DHCP vs Static IP)
DHCP Bring-Up Flow (Used in This Demo)
Advantages:
Zero manual IP configuration
Works in typical home/office networks
Ideal for education and demos
Static IP Bring-Up Flow (For Comparison)
Static IP works only if:
IP does not conflict
PC is on the same subnet
For beginners, DHCP is safer.
4. Role of W5500 in Network Bring-Up
The W5500 handles:
ARP
IP
TCP state machine
Retransmission
Checksum calculation
The MCU (ESP8266 or STM32) only:
Configures registers
Reads socket state
Moves data in/out of buffers
This is why W5500 is ideal for learning TCP server concepts without drowning in protocol details.
5. ESP8266 vs STM32: Same Concept, Different MCUs
ESP8266
Often used in education
Wi-Fi capable, but Ethernet via W5500 is deterministic
Good for demonstrating TCP server basics
STM32
Common in industrial products
Precise timing
Clean SPI control
Long-term stability
Key point:
The W5500 TCP server logic is identical on both platforms.
6. TCP Server Socket Lifecycle on W5500
Conceptual Socket State Flow
Important rules:
Socket must be in LISTEN to accept connections
Only one client per socket
RX buffer must be drained
RECV must be issued after reading data
Most TCP server bugs happen here, not in DHCP.
7. Typical TCP Server Data Flow
RX Path
TX Path
Failure to manage RX/TX pointers correctly results in:
One-time success
Then “no data received” symptoms
8. Common Beginner Mistakes (And Why They Happen)
❌ “TCP server doesn’t respond”
Cause:
Device never got a valid IP (DHCP failed)
❌ “Client connects once, then fails”
Cause:
RX buffer not released (RECV missing)
❌ “Works on router, not direct cable”
Cause:
No static IP configuration on PC
These are network bring-up issues, not TCP problems.
9. Educational Value of This Demo
This demo is valuable because it teaches:
Real TCP server behavior
Role of routers and DHCP
Difference between link-up and IP-ready
How embedded devices become discoverable
It avoids:
Complex cloud protocols
Hidden software stacks
Black-box behavior
10. Engineer Takeaway
A W5500 TCP server is not just about sockets — it is about correct network identity and reachability.
DHCP + router:
Solve IP management
Reduce configuration errors
Make demos reproducible
This is why DHCP is required in this educational setup.
FAQ (Engineer-Grade)
Q1. Can I use static IP instead of DHCP?
Yes, but you must configure both device and PC correctly.
Q2. Is a router mandatory for TCP server?
Only if you rely on DHCP. Static IP can work without it.
Q3. Does W5500 implement DHCP?
No. DHCP client logic runs on the MCU.
Q4. Is this suitable for industrial products?
Yes. Many products start with DHCP, then move to static IP.
Q5. Does ESP8266 vs STM32 change TCP behavior?
No. TCP behavior is handled by W5500 hardware.
Source
Bilibili video: BV1ek4y1s7fL
WIZnet W5500 Datasheet
Tags
W5500, TCP Server, DHCP, ESP8266, STM32, Network Bring-Up, Embedded Ethernet, Education
🇰🇷 한국어 번역 (1:1 Full Translation)
W5500 TCP 서버는 DHCP 환경에서 어떻게 동작하는가?
ESP8266과 STM32를 활용한 엔지니어 관점 네트워크 브링업 설명
요약
본 문서는 WIZnet W5500을 사용해 TCP 서버를 구현할 때 DHCP 기반 네트워크 환경이 왜 필요한지를 설명한다. ESP8266과 STM32 플랫폼을 예로 들어, 네트워크 브링업, 라우터 의존성, TCP 서버 소켓 동작을 단계적으로 분석한다.
1. TCP 서버의 의미
TCP 서버는
연결을 기다리는 쪽이다.
2. DHCP가 필요한 이유
라우터는
IP를 배포하고
네트워크를 성립시킨다.
3. 브링업 흐름
DHCP → IP 획득 → LISTEN
4. W5500의 역할
TCP/IP는
하드웨어가 처리한다.
5. 흔한 실수
IP 미할당
RECV 누락
라우터 없이 연결
6. 핵심 메시지
W5500 TCP 서버의 핵심은 소켓이 아니라 네트워크 도달성이다.
태그
W5500, TCP 서버, DHCP, ESP8266, STM32, 네트워크 브링업, 임베디드 이더넷