---
title: "TCP window size setting"
url: "https://maker.wiznet.io/forum/13109"
markdown_url: "https://maker.wiznet.io/forum/13109/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "zbigelpl"
created: "2018-11-08T23:10:05+09:00"
last_activity: "2018-11-09T09:17:11+09:00"
language: "en"
views: 616
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# TCP window size setting

## Question

Asked by zbigelpl on 2018-11-08 in Ethernet Chips.

Hi
I’ve found somewhere informtion that it is set indirectly by choosing RMSR(RX Memory Size Register). So for instance setting RMSR to 0x03 makes RX buffer 8kB size for Socket0. Does it make TCP window size 8kB as well?
Is there any way to set TCP window size directly when w5100 operates as TCP server?

Thanks
Zbigniew

## Replies

### Reply 1 by becky, 2018-11-09

Hello,

Setting RMSR to 0x03 makes RX buffer 8KB and Window Size 8KB for Socket 0.
Thanks

### Reply 2 by zbigelpl, 2018-11-09

Thanks a lot for confirmation

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Source: https://maker.wiznet.io/forum/13109