---
title: "TCP Client Connection Problem"
url: "https://maker.wiznet.io/forum/9474"
markdown_url: "https://maker.wiznet.io/forum/9474/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "mettiblack72"
created: "2024-09-22T21:43:33+09:00"
last_activity: "2024-09-22T21:53:44+09:00"
language: "en"
views: 3
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# TCP Client Connection Problem

## Question

Asked by mettiblack72 on 2024-09-22 in Ethernet Chips.

Hello ,
I'm working with W5500 as Client , I know in client mode w5500 should send Connect command and then send/receive data and then disconnect socket ,

Our Server is PLC and we want to read some data from PLC, My problem is sometimes w5500 doesn't receive SYN/ACK packet from server side then we can't connect to PLC and sometimes got it ! 75% of our test are successful connection but sometimes we have problem, what should I do for this problem ?

In w5500 datasheet page 46 -> Connect partition -> number 2 , the reason of connection fail are explained, but my another question is if we have error in connection, what should programmer do to handle it ? should I send Connect command again ??

![](https://maker.wiznet.io/upload/ckeditor5/6779380%5F1727041278%2Epng)

## Replies

### Reply 1 by mettiblack72, 2024-09-22

if w5500 reaches to RTR value , default value is 200ms , does w5500 resend SYN packet to server automatically ?

and because RCR is 8 , w5500 resend SYN packet 8 times to server ?

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Source: https://maker.wiznet.io/forum/9474