---
title: "sock_send()"
description: "The sock_send() function is used to send a message on a socket. It is similar to the send function in POSIX, but it also supports writing the data from multiple buffers in the manner of writev."
url: "https://wasix.org/docs/api-reference/wasi/sock_send/"
markdown: "https://wasix.org/docs/api-reference/wasi/sock_send.md"
---

# `sock_send()`

Send a message on a socket.

## Description

The `sock_send()` function is used to send a message on a socket. It is similar to the `send` function in POSIX, but it also supports writing the data from multiple buffers in the manner of `writev`.

The function sends a message using the provided scatter/gather vectors. It retrieves the data from the buffers specified by the scatter/gather vectors and transmits it on the socket. The number of bytes transmitted is returned.

## Syntax

```ebnf
  ;;; the data from multiple buffers in the manner of `writev`.
  ;;; Note: This is similar to `send` in POSIX, though it also supports writing
  ;;; Send a message on a socket.
  (@interface func (export "sock_send")
    (param $fd $fd)
    ;;; List of scatter/gather vectors to which to retrieve data
    (param $si_data $ciovec_array)
    ;;; Message flags.
    (param $si_flags $siflags)
    ;;; Number of bytes transmitted.
    (result $error (expected $size (error $errno)))
  )
```

## Parameters

- `ctx`: A mutable reference to the function environment.
- `sock`: The file descriptor of the socket to send on.
- `si_data`: A list of scatter/gather vectors containing the data to be sent.
- `si_data_len`: The length of the scatter/gather vector list.
- `si_flags`: Message flags.
- `ret_data_len`: A pointer to store the number of bytes transmitted.

## Return Value

The function returns a `Result` containing an `Errno` value. If the operation is successful, `Errno::Success` is returned. Otherwise, an appropriate `Errno` value indicating the error is returned.

## Notes

- The `sock_send()` function sends a message on a socket using the provided scatter/gather vectors.
- The function supports writing the data from multiple buffers.
- The `si_data` parameter represents a list of scatter/gather vectors, where each vector contains a buffer and its length.
- The `si_data_len` parameter specifies the length of the scatter/gather vector list.
- The data to be sent is retrieved from the buffers specified by the scatter/gather vectors.
- The number of bytes transmitted is stored in `ret_data_len`.
- The specific behavior of the `sock_send()` function may vary depending on the runtime environment and underlying networking implementation.

---

[Documentation index](https://wasix.org/llms.txt) · [HTML version](https://wasix.org/docs/api-reference/wasi/sock_send/)