---
title: "The existing connection was forcibly closed by the remote host w5300"
url: "https://maker.wiznet.io/forum/12115"
markdown_url: "https://maker.wiznet.io/forum/12115/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "linask"
created: "2017-01-27T16:46:50+09:00"
last_activity: "2017-05-04T08:39:41+09:00"
language: "en"
views: 806
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# The existing connection was forcibly closed by the remote host w5300

## Question

Asked by linask on 2017-01-27 in Ethernet Chips.

Hello,
I made visual basic app for testing Rx Tx performance with ability to use it as set/get register type communication over the LAN, but when i try to ask large buffers to send and to receive, i get "the existing connection was forcibly closed by the remote host " error

with small packets like 10kx8b it is running fine, but if i make 40kx8b, it will generate this error.

Note that i have only one socket with 64 for Tx, 64 for Tx FIFO size, so i can use 65536 sized massage, and indeed i can if only it is transmitting or receiving.

But even bigger problem, that i could not connect to w5300 with computer, it just say connection was refused by host, while my program on stm32f4 is happily running socket switch program with SOCK_LISTEN register active, just like after restart.

If i make reset and config it again, it start to work.

Question, how can i know that client can’t connect even if i am in SOCK_LISTEN mode, just like it suppose to be ? and how to fix it ?

[short video in youtube:](https://www.youtube.com/watch?v=DuiGD0YWePM)

## Replies

### Reply 1 by linask, 2017-01-27

ok, si i get exception that says that SOCKET is not created!. (when i try do LISTEN listen(0))

but at the same time, i can’t create it, it is just stuck at that. Any idea how to solve it ?

### Reply 2 by Eugeny, 2017-01-28

Download this document [url][http://www.wiznet.co.kr/wp-content/uploads/wiznethome/Chip/W5100/Document/W5100_Datasheet_v1.2.6.pdf\[/url\]](http://www.wiznet.co.kr/wp-content/uploads/wiznethome/Chip/W5100/Document/W5100_Datasheet_v1.2.6.pdf%5B/url%5D) and study page 29 (socket status register) and chapter 5 (functional description). These chapters will give you understanding about socket workflow for W5x00 family, and how to handle chip’s registers.

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Source: https://maker.wiznet.io/forum/12115