---
title: "W5500 in Webserver mode refuse to connect by Inetrnet Browser Renasas RX65N565NEDxFP"
url: "https://maker.wiznet.io/forum/15622"
markdown_url: "https://maker.wiznet.io/forum/15622/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "lengyelaronjozsef"
created: "2025-03-08T18:47:03+09:00"
last_activity: "2025-03-08T18:47:03+09:00"
language: "en"
views: 2
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# W5500 in Webserver mode refuse to connect by Inetrnet Browser Renasas RX65N565NEDxFP

## Question

Asked by lengyelaronjozsef on 2025-03-08 in Ethernet Chips.

Hello everyone,
At the moment I work with a Wiznet W5500 Ethernet module. With Arduino Uno it works nicely as a webServer.
I was thinking that I would like to use the W5500 module with another microcontroller, practically a Renesas RX65N565NEDxFP TargetBoard RX65N V1.12. I studied the datasheet of the W5500 and I can read and write the registers of the module through the SPI bus.
My goal is to have a very simple Webserver according to TCP protocol. I set all the important parameters: IP address, source Port number = 80, I set the subnet mask, the network gateway . I pinged the moddul that's okay too. -------- Now the problem begins: According to the Internet Chrome browser, the module refuses to connect----- , there is no network parameter conflict. The module is connected to the desktop computer via a TP-Link router. My respectable question is, what causes the connection rejection by the W5500 module? The "communication rate" of the Renesas RX65N565NEDxFP SPI peripheral is therefore the SPI_Transfer baud rate : 8000 Kb/s. The clock signal of the peripherals on the Renesas microcontroller side is 60MHz . So in summary, my honorary question would be, what is the reason for the connection to be rejected from the W5500 side? Thank you very much in advance for your help everyone!

Sincerely, : L e n g y e l Jozsef , Central Europe , Hungary .

## Replies

### Reply 1 (verified answer) by WIZnet AI assistant (automated answer), 2025-03-08

Hello Lengyel József, Thank you for reaching out about your W5500 Ethernet module connection issue with the Renesas RX65N microcontroller. Based on your description, you've successfully set up the basic configuration and can ping the module, but the web server connection is being rejected. There could be several reasons for this issue: 1. Socket Configuration: Make sure you've properly initialized a socket for the web server. You need to: - Open a socket in TCP mode - Set it to LISTEN state for a web server - Ensure the socket is bound to port 80 2. Socket Status Checking: After attempting to establish a connection, check the socket status register to see if it's in the ESTABLISHED state or if there's an error code. 3. Buffer Management: The W5500 has internal TX/RX buffers that need to be properly managed. Ensure you're correctly reading from and writing to these buffers. 4. Interrupt Handling: If you're using interrupts, verify they're properly configured and handled. 5. SPI Communication: While your SPI speed (8 Mbps) should be adequate, there might be timing issues. Try reducing the SPI speed temporarily to see if that helps. 6. Command Sequence: The W5500 requires specific command sequences for operations. Double-check that you're following the correct sequence for socket operations. 7. TCP Keep-Alive: If enabled, ensure it's properly configured. For debugging, I recommend: - Monitoring the socket status registers to see what state the socket is in when a connection attempt is made - Using a network analyzer like Wireshark to see the TCP handshake process - Implementing a simple response to verify basic functionality before building a complete web server You might also want to check out WIZnet's official documentation and examples for the W5500 at https://docs.wiznet.io/Product/iEthernet/W5500/overview, which includes detailed information on register settings and socket programming. WIZnet AI Support Team

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Source: https://maker.wiznet.io/forum/15622