---
title: "add bytes to TX_Buffer while W5500 is sending TCP"
url: "https://maker.wiznet.io/forum/13808"
markdown_url: "https://maker.wiznet.io/forum/13808/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "Julio Beloso"
created: "2020-05-05T14:40:54+09:00"
last_activity: "2020-05-20T04:04:40+09:00"
language: "en"
views: 425
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# add bytes to TX_Buffer while W5500 is sending TCP

## Question

Asked by Julio Beloso on 2020-05-05 in Ethernet Chips.

Hi,

I would like to know if I can add more bytes to the buffer with “wiz_send_data()” if there is any free size while command SEND is running in chip (it is no finished yet (sock_is_sending = true))

If I can, Can I call to SEND command again while W5500 is still sending?

Regards

## Replies

### Reply 1 by becky, 2020-05-20

We don’t recommend to call send command while w5500 is still sending.
Please add a buffer and send again after sending previous data is completed.

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Source: https://maker.wiznet.io/forum/13808